SN 1054
Encyclopedia
SN 1054 is a supernova
that was first observed as a new "star" in the sky on July 4, 1054 AD, hence its name, and that lasted for a period of around two years. The event was recorded in multiple Chinese
and Japan
ese documents and in one document from the Arab world
. While it has been hypothesized that SN 1054 was also observed by American-Indian tribes and Europeans, it has not been conclusively proven.
The remnant
of SN 1054, which consists of debris ejected during the explosion, is known as the Crab Nebula
. It is located in the sky near the star Zeta Tauri
(ζ Tauri). Some of the remnant of the explosion formed a pulsar
, called the Crab Pulsar
(or PSR B0531+21). The nebula and the pulsar it contains are the most studied astronomical objects outside the Solar System
. It is one of the few Galactic
supernovae where the date of the explosion is well known. The two objects are the most luminous in their respective categories. For these reasons, and because of the important role it has repeatedly played in the modern era, SN 1054 is the best known supernova in the history of astronomy.
The Crab nebula is easily observed by amateur astronomers thanks to its brightness, and was also catalogued early on by professional astronomers, long before its true nature was understood and identified. When the French astronomer Charles Messier
watched for the return of Halley's Comet in 1758, he confused the nebula for the comet, as he was unaware of the former's existence. It was because of this error that he created his catalogue of non-cometary nebulous objects, the Messier Catalogue, to avoid such mistakes in the future. The nebula is catalogued as the first Messier object, or M1.
e, comets, and later, the supernovae.
The first people to attempt a systematic compilation of records from China were the father and son Biot. In 1843, the sinologist Édouard Biot
translated for his father, the astronomer Jean-Baptiste Biot
, passages from the astronomical treatise of the 348 volume Chinese encyclopaedia, the Wenxian Tongkao
.
Almost 80 years later, in 1921, Knut Lundmark
undertook a similar effort based on a greater number of sources. In 1942, Jan Oort
, convinced that the Crab Nebula was the "guest star" of 1054 described by the Chinese, asked sinologist Jan Julius Lodewijk Duyvendak, to help him compile new evidence on the observation of the event.
of the Song dynasty
(960-1279). The relevant year is recorded in Chinese documents as "the first year of the Zhihe era". "Zhihe" was an era name
used during the reign of Emperor Renzong, and corresponds to the years 1054-1056 C.E., so the first year of the Zhihe era corresponds to the year 1054 C.E.
Six accounts from China relate the observation of the phenomenon. Like almost all of the records relating to the guest star, none of them are first hand: the oldest was about a century after the apparition of the star. Some of these accounts are nevertheless remarkably well preserved, and are used to reconstruct the essential information concerning the observation of the explosion.
is the first East Asian source that came to the attention of Western astronomers; it was translated by Édouard Biot in 1843. This source, compiled by Ma Duanlin
in 1280, is relatively brief. The text states:
"Tianguan" is the traditional Chinese name for Zeta Tauri
.
"), a book covering the period of 960-1126 and written 40 years or so later by Li Tao (1114–1183), contains the oldest Chinese testimonies relating to the observation of the star. It was rediscovered in 1970 by the specialist in Chinese civilisations Ho Peng Yoke and collaborators.
It is relatively imprecise in the case of the explosion of SN 1054. A loose translation of what was stated :
s, and as such are important sources supplementing the official Twenty-Four Histories
. The Song dynasty had a specific government department dedicated to compiling the Huiyao, and some 2,200 volumes were published in ten batches during the Song dynasty. However, most of these documents were lost by the time of the Qing Dynasty
except for the synopsis and a relatively small portion preserved as part of the imperial Yongle Encyclopedia
. In 1809, the portion preserved in the Yongle Encyclopedia was extracted and re-published as the Song Huiyao Jigao (the "draft extract of the Song Huiyao"). Subsequent scholars have worked on the project further and the current edition dates from 1936.
This document recounts the observation of the guest star, by focusing on the astronomical aspect, but gives more important information relating to the visibility of the star, by day and by night.
In chapter 56 ("Astronomical treaty") of the same document, the guest star is again mentioned in a chapter dedicated to this type of phenomenon, this time focusing on its appearance, and this is in terms very close to Wenxian Tongkao :
, which ruled in the area around Manchuria
from 907-1125. The book in question, the Qidan Guozhi, was compiled by Ye Longli in 1247. It includes various astronomical notes, some of which are clearly copied from the Song Shi. This entry referring to the star of 1054 seems unique:
Three of these accounts clearly emanate from the same source: those of Wenxian Tongkao, of Xu Zizhi Tongjian Changbian, and of chapter 56 of Songshi, who had evaluated the angular distance from the star to Tianguan according to the formula "perhaps several inches away". The three documents however are in apparent disagreement about the date of appearance of the star. Two mention the day jichou, and the third, the Xu Zizhi Tongjian Changbian, the day yichou. These terms refer to the Chinese sexagenary cycle, corresponding to numbers 26 and 2 of the cycle, which corresponds, in the context where they are cited, respectively, to July 4 and June 10.
The latter date is considered incorrect for several reasons. On the one hand, the terms yichou and jichou are different from one and other by only one character, the first, and these characters are very similar, yichou and jichou written respectively 乙丑 et 己丑, so a typographical error in re-transcription seems possible. For others, the entries of Xu Zizhi Tongjian Changbian follow a strict chronological order, and previous entries also refer to the Chinese sexagenary cycle, concerning the days yiyou (22) and bingxu (24), while later entries relate to the days yiwei (32, part of the sixth lunar moon), bingshen (33), then renyin (39). In this context, it seems far more likely that the use of yichou is a result of an error in re-transcription rather than a chronological misplacing of the entry. The duration of visibility is explicitly mentioned in chapter 12 of Songshi, and slightly less accurately, in the Song Huiyao, the last sighting was the 6th of April 105613, after a very long period of visibility of 642 days. This duration is supported by the Wenxian Tongkao and chapter 56 of the Songshi. According to the Song Huiyao the visibility of the guest star was for only 23 days, but this is after mentioning visibility during daylight. This period of 23 days applies in all likelihood solely to visibility during the day.
The account of Qidan Guozhi alluded to the notable astronomical events that preceded the death of King Xingzong. Various historical documents allow us to establish the date of death of the Emperor Xingzong as the 28th of August 1055, during the eighth lunar month of the twenty-fourth (and not twenty-third) year of his reign. The dates of the two astronomical events mentioned (the eclipse and the appearance of the guest star) are not specified, but were probably before the obituary (2 or 3 years at most). Two solar eclipses were visible shortly before that date in the Khitan kingdom, on the 13th of November 1053 and the 10th of May 1054. Of these, only one occurred around noon, that of the 13th of November, it seems likely that this is what the document mentions. As for the guest star, only a rough estimate of location is given, corresponding to the moon mansion Mao. This mansion is situated just east of where the star appeared, as mentioned in the other testimonies (see the section General localisation of the Event below). Since no other known significant astronomical event occurred in this region of the sky during the two years that preceded the death of Xingzong, it seems likely that the text is actually referring to the star of 1054.
The location of the guest star can in principle be deducted from the statement “to the south-east of Tianguan, perhaps several inches away “, which for a long time perplexed modern astronomers, because if Tianguan is almost universally regarded as a correspondent for the star Zeta Tauri
(ζ Tauri), the Crab nebula, following a clearly old explosion of stars about 1000 years ago, and therefore a natural candidate for this guest star, is not situated in the south-east but to the north-west of this star (see the General localisation of the Event section below).
(1162–1241), a poet and courtier, mentions the guest star of 1054 in his famous diary, the Meigetsuki. Better known for his literary works than for his interest in astronomy, he supplied the most detailed description of the supernova of 1054.
His interest in the guest star seems to have come accidentally whilst observing a comet in December 1230, which prompted him to search for evidence of past guest stars, among those SN 1054 (as well as SN 1006
and SN 1181
, the two other historic supernovas from the early second millennium). The entry relating to SN 1054 can be translated as:
SN 1054 in Meigetsuki is not a historical record.It was mentioned about relations between the guest stars and ominous incidents,it was a onmyodo superstition.As a result,he concluded that there Are relations between them.
The source used by Fujiwara no Teika is the records of Yasutoshi Abe(Onmyōdō doctor), but it seems to have been based, for all the astronomical events he has recorded, on documents of Japanese origin. The date he gives is prior to the third part of ten days of the lunar month mentioned, which corresponds to the period of between 30 May and the 8th of June 1054 of the Julian calendar, which is around one month earlier than Chinese documentation. This difference is usually attributed to an error in the lunar months (fourth place and fifth place). The location of the guest star, clearly straddling the moon mansions Shen and Zuixi, corresponds to what would be expected of a star appearing in the immediate vicinity of Tianguan.
« Era of Tengi of the Emperor Go-Reizei, second year, fourth lunar month. A guest star was seen. »
The brevity contrasts with the more detailed descriptions of “guest stars” (actually supernovas) of 1006 and 1181. The reason for the little detail on the entry of 1054 is not known. Like the other two Japanese mentions of the star, it mentions the fourth month and not the fifth.
and SN 1181
) reveals a close proximity in the dates of discovery of a guest star in China and Japan, although clearly based on different sources. Considering the mention of the fourth lunar month it would then be accurate to imagine that in that event, the Japanese have significantly outperformed their Chinese counterparts, a mystery for which an explanation is not forthcoming.
The Japanese documents do not specify the visibility in daylight, but compare it to Jupiter, which is visible in daylight, and reports of which appear in the astronomical records of the contemporary Chinese world.
The visibility in daylight as described by the Chinese texts is thus validated by the Japanese Documents, and is consistent with a period of moderate visibility, which implies that the star's period of diurnal visibility was very short, even during favourable conditions for observation (a star visible during of sunrise is relatively easy to spot if its position is known and as the background sky becomes more and more luminous).
, which was significantly brighter, was mentioned by several Arab chroniclers, there exist no Arab reports relating to the rather faint SN 1181
. Only one Arab account has been found concerning SN 1054, whose brightness is between those of the last two stars mentionned. This account, discovered in 1978, is that of a Nestorian Christian doctor, Ibn Butlan
, transcribed in the Uyun al-Anba, a book compiled by Ibn Abi Usaybi'a (1194–1270) in the mid-thirteenth century. This is the passage in question :
The three years cited (445, 446, 447) refer, respectively, to: 23 April 1053-11 April 1054, 12 April 1054-1 April 1055, and 2 April 1055-20 March 1056. There is an apparent inconsistency in the year of occurrence of the star, first announced as 446, then 445. This problem is solved by reading other entries in the book, which quite explicitly specify that the Nile was low at 446.This year of the Muslim calendar ran from the 12th of April 1054 to the 1st of April 1055, which is compatible with the appearance of the star in July 1054, as its location (admittedly rather vague), is in the astrological sign of Gemini (which, due to Axial precession, covers the eastern part of the Constellation Taurus).The date of the event in 446 is harder to determine, but the reference to the level of the Nile refers to the period preceding its annual flood, which happens during the summer.
These attempts at linking a genuine celesatial event to very imprecise documents have been strongly criticised by a number of authors, who view them a seeking to promote the existence of sightings of the event in Europe and as being "anxious to ensure that this event was recorded by Europeans". The lack of accounts from European chroniclers has long raised questions. In fact, it is known that supernova of 1006
was recorded in a large number of European documents, albeit not in astronomical terms. Among the proposed explanations for the lack European accounts of SN 1054 is its concurrence with the East-West Schism
is prominent. In fact, the date of the excommunication of the Patriarch of Constantinople
Michael I Cerularius
(16 July) corresponds to the star reaching its maximum brightness and being visible in the daytime. This is only an unverifiable hypothesis, and it is difficult to explain how an account of an event which was visible a priori to everyone could have disappeared without a trace. The fact is however, that European documents of the 11th century were written by people who, despite their extensive learning, possessed extremely limited knowledge of astronomy, and could not even consistently recognise the stars which form various astronomical conjunctions (see examples below).
The date that this passage was written is not specified, but in it, there is a reference to an earthquake
in Brescia
, which has been identified as taking place on 11 April 1064. Dall'Olmo did not propose any explanation of this apparent mismatch of ten years between the supernova and the earthquake, besides the hypothesis that it could be the result of a transcription error. Even if this were not the case, the absence of a precise date and position makes the phenomenon difficult to identify, and it could simply be a conjunction
between the moon
and a planet (probably Venus or Jupiter), or a concealment of a planet by the moon.
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, the Cronaca Rampona. This text, a subject of astronomers' attention since 1972, was interpreted as a possible sighting of the supernova in 1981, and again in 1999. The part of the chronicle that was highlighted indicates that:
“ In the year of Christ Ml8, Pope Stephen IX
has come to the throne [...] Also in this year of Christ Ml8, Henry III
reigned [or “ lived ”] for xl9 years. He went to Rome for the first time in the month of May. At this time, famine and death was upon the whole world. He stayed in the province of Tibur
for three days in the month of June [...] At that moment, a very brightly-shining star entered into the circle [or the circuit] or the new moon, in the thirteenth Calends at the beginning of the night The interesting part of the Latin text says stella clarissima in circuitu prime lune ingressa est, 13 Kalendas in nocte initio
Without even discussing the last, astronomical part of the text, skeptics point out at least two discrepancies in the following : Pope Stephen IX
became Pope in 1057, not 1058, and Emperor Henry III who is mentioned, actually Henry III, Holy Roman Emperor
, was born in 1017, 39 and not 49 years before 1058, his reign having started in 1039 (King of the Romans
, then as emperor of the Romans from 1046 after being consecrated by Pope Clement II during the course of his brief pontificate). Henry III, therefore, was dead in 1056, and his reign could not have coincided with that of Stephen IX. It seems more likely that the text was the subject of various alterations, as the date format (for example “ Ml8 ” for 1058, the second character of “ Ml8 ” being the lower case letter L), with a mix of Roman (upper and lower case) and Arab characters, was common in the period when the Cronaca Rampona was written (15th century) but not that of the supernova four centuries earlier. Furthermore, associating the event described with the sighting of a supernova in 1054 would require the supposition that the Cronaca Rampona entry was in the wrong place in relation to the rest of the document, as the different entries are in chronological order and several previous entries are later than 1054 ( in order, the previous entries refer to 1046, 1049, 1051, 1055, 1056, written in a mix of Arab and Roman characters, namely Mxl6, Mxl9, Mli, Mlv and Ml6). Additionally, there is a discrepancy with the date of the new moon. The term Calends, which refers to the Roman calendar
, can be written in the ordinary form of the Gregorian calendar
, and the phase of the moon can be calculated from it. It is clear that the new moon did not occur on the thirteenth day of the Calends in any month in 1054.Historically, the Kalendes were based on the phases of the Moon, the start of a Kalende corresponded with a new moon
. Par la suite un décalage s'opéra avec la phase de la Lune, mais la position de celle-ci varie lentement d'une Kalende à l'autre. So no month from December 1050 to May 1056 had a new moon fall on the 13th of the month. All of this is in strong opposition to the precision of the dates of references to eclipses in medieval European chronicles : a study of 48 partial or total solar eclipse
s from 733 to 1544, reveals that 42 dates out of 48 are correct, and of the six remaining, three are incorrect by one of two days and the three others give the correct day and month, but not the year. Finally, even considering that the stated event corresponds to May or June 1054 nevertheless, and describes a conjunction between the already visible supernova and the moon, another problem arises : during those months, the moon did not pass very close to the location of the supernova. Incidentally, the vocabulary used in the Latin text is somewhat unusual. The Latin word translated into English as circle is circuitu, used in place of the more commonly used circulus, but this semantic variant does not seem to change the sense of the text, which, in all possible translations of circuitu, suggests an object which is found on or close to the moon's path of travel.
Therefore, it is possible that the account describes an approach or a concealment of a planet by the moon, contemporary to the suggested date (1058). This scenario is corroborated by two contemporary documents which are perfectly dated and describe a conjunction and a planetary concealment by the moon in relatively similar terms. These two documents, unearthed by Robert Russell Newton
, are taken from the Annales Cavenses, Latin chronicles from la Trinità della Cava
(Province of Salerno
, Southern Italy
). They mention a “bright star that entered into the circle of the new moon” [Martii incipiente nocte] stella clarissima in circulum lunae primae ingressa est for 17 February 1086 and stella clarissima venit in circulum lunae for 6 August. on dates corresponding to 17 February 1086 and 6 August 1096. Calculations indicate that Venus was eclipsed by the moon for half an hour on the 17th February. On the 6th August, Jupiter passed to less than one degree from the moon after a lunar eclipse
which was also mentioned in the chronicle. The fact that the chronicler or chroniclers did not realise that they had seen a planet rather than a new star demonstrates the weak astronomical knowledge of the scholars of the time, whose astronomical accounts are actually very difficult to interpret and attribute to a rare event.
town of Oudenberg, describes the death of Pope Leo IX
in Spring 1054.
The date described corresponds to the 14th April 1054, the “ second day of the week ” being a Monday, according to the custom of the time. This simple date causes several problems : numerous historical documents describing the death of the Pope state the date as the 19th April and not the 14th. Additionally, neither of these days were Mondays. The astronomical part of the text is also difficult to interpret and associate with the supernova. The description of the phenomenon, which is difficult to identify, is very brief, which contrasts with the timescale of a supernova. Il is not given a location in the sky and the time of the sighting is not given, not even whether it was during the day or the night. There are a priori numerous optical or atmospheric phenomena which can impress a chronicler who is not a specialist in astronomy, such as aurora
s (at night) or a solar halo
(in the daytime). Most importantly, the reference to “ everywhere on earth ” could correspond to a non-localised event, but it is not possible to know the exact meaning of such a reference.
(Umbria
north of Rome
). He seems to have confirmed seeing :
The nature of the observed phenomenon is difficult to identify, as the subject is enshrouded in mystery. Certain authors have proposed that he actually described the supernova. A favourable moment would have been at dusk, when the sun was setting before the star ζ Tauri. However, on that night, a concentration of planets was in that area of the sky : Mars
, Mercury
, Venus
, and Jupiter
slightly further away. That area of the sky is also rich in bright stars (the constellation of Orion
, Sirius
, Capella
etc.), and it is possible that these, along with the planets, formed the “ countless lamps ” in Albertus' account. Considering this vast concentration of brightness, the supernova's presence would not have been remarkable. Just like the preceding account, this text directly links the death of the Pope to an “ extraordinary ” event, which could have been done to justify a miracle associated with the deceased, in order to facilitate his canonisation (which was carried out by Pope Victor III
in 1087).
n chronicles. One of the authors stated some years later that one of the documents could correspond to a sighting of the supernova of 1054. According to his translation of the document, it indicates :
This brief description strongly suggests a closening or concealment of a planet or bright star by the moon. In fact, calculations indicate that on the date mentioned, the moon got closer by around 3 degrees, when Cancer
was in conjunction with Jupiter, a fact which the theorists advocating a sighting of the supernova failed to verify or even mention.This conjunction is not in the article of Collins et al., which actually claims to have calculated the event as occurring on the night of 11th May 1054.
In a more general manner, these documents are not actually astronomical, but produced by learned chroniclers who had limited astronomical knowledge. This is evident in the most workable document, the Armenian chronicle, where the usual conjunction between the moon and Jupiter is not recognised as such, as is the case for numerous other conjunctions.For example those in the aforementioned Annales Cavenses.
and his colleagues proposed a radical reinterpretation of the European documents and claimed that they convincingly indicate that the Europeans had seen the supernova well before Chinese astronomers.
Concerning the Chinese documents, they point out their various date errors (see above) as proof that the quality of their observations was inferior to what is commonly accepted, and therefore that nothing rules out the possibility that more hardened observers may have seen the supernova beforehand. They also make their point by bringing up the problem of the localisation of the supernova in relation to the star ζ Tauri (see below). Finally, based on a controversial translation of the document from khitan people, they claim that the supernova was probably visible at the time of the solar eclipse of 10 May 1054.
In the opposite way, they reinterpret the European documents as relatively corroborating in relation to the fact that a notable astronomical event occurred in Spring 1054, before the conjunction between the supernova and the sun. They believe that the metaphoric aspect of certain documents only reflects the observers' limited knowledge of the sky, without prejudicing their ability to observe., Furthermore, they claim that the date problems in the Cronoca Rampona are not errors, as the European chroniclers are not interested in being very precise concerning dates. They also mention, without further elaboration, that the Chinese observations of guest stars was primarily of an astrological, and not scientific, nature, which could make their content biased.
As for the reference to the supernova in d'Ibn Butlan scripture, they trust the date of 445 in the Muslim calendar (23 April 1053 — 11 April 1054) and not 446 (12 April 1054 — 1 April 1055) to confirm that the supernova was visible from April 1054, without taking into account the fact that other parts of the scripture are more coherent with the date of 446, not 445.
The works of Collins et al. were strongly criticised by F. Richard Stephenson
and David A. Green, who pointed out a lack of seriousness in the analysis of their colleagues. Notably, they insist that date problems in Asian documents are easily resolved. One of them (the Xu Zizhi Tongjian Changbian) corresponds in a relatively obvious way to a typographic error, and the other (the month of observation of Japanese documents) to a common date error in this set of documents. They mention that claiming that the supernova was visible at the time of the solar eclipse on May 10, 1054 is based on an inappropriate interpretation of the translation and is contrary to astronomical reality. In fact, this eclipse having only been partial, no star close to the sun could have been seen at that time. Finally, they insist on the lack of astronomical knowledge of the European chroniclers compared to the Chinese atronomers. According to them, this point makes it difficult to attribute these documents to an observation of the supernova. If this was the case, it would be necessary to explain why no European document mentions the supernova in Summer, when it was perfectly visible according to the Chinese documents, and how the more experienced Chinese and Japanese observers could have missed the supernova at this time. They also note that even in the case of a concordance of dates, nothing proves that events which occurred in the same year correspond to a single astronomical phenomenon. The guest stars of 837 are an example of two different novas which occurred in the same year (additionally marked by the spectacular passing of Halley's comet). The four guest stars of 1592 reinforce this comment. Green and Stephenson's conclusions add to previous works dating from 1995 where the different European observations had already been rejected due to their lack of precision and the impossibility to draw clear astronomical sense from them.
The thesis of Collins et al. was not broadly taken up in scientific literature afterwards,The ADS
database only includes three articles that cite this reference: (list) but has nevertheless enjoyed a certain visibility to the general public, notably being taken up by the magazine Ciel & Espace with a certain enthusiasm.
Two Native American
paintings in Arizona
show a crescent moon located next to a circle that could represent a star. It has been proposed that this represents a conjunction between the moon and the supernova, made possible by the fact that, seen from the Earth
, the supernova occurred in the path of the Ecliptic
.
This theory is compatible with the datings in these paintings. In fact, on the morning of 5 July, the moon was located in the immediate proximity of the supernova, which could reinforce the idea that it was this proximity that had been represented in these paintings. This interpretation cannot be confirmed. The dating of the paintings is extremely imprecise (between the 10th and 12th century), and only one of them shows the crescent moon with the correct orientation in relation to the supernova. Moreover, this type of drawing could well represent a proximity of the moon with Venus
or Jupiter
.
Another, better known document was updated during the 1970s at the Chaco Canyon
site (New Mexico
), occupied around 1000 AD by the Anasazi
. On a vertical surface plane of a construction, it represents a hand, below which there is a crescent moon facing a star at the bottom-left. On the ground in front of the petroglyph there is a drawing which could be the core and tail of a comet. Apart from the petroglyph, which could represent the configuration of the moon and supernova on the morning of 5 July 1054, this period corresponds to the apogee of the Anasazi civilisation. It seems possible to propose an interpretation of the other petroglyph, which, if it is more recent than the other one, could possibly correspond to the passing of Halley's Comet in 1066. Although plausible, this interpretation is impossible to confirm and does not explain why it was the supernova of 1054 that was represented, rather than the supernova of 1006
, which was brighter and also visible to this civilisation.
(asterism
in Western astronomical science) called Tianguan by Chinese astronomers.
The constellations (asterisms) of Chinese astronomy are generally smaller than the constellation
s of the western world, and some of these named "asterisms" can consist of a single star. They were catalogued around the 2nd century BC. Depending on the brightness of the stars and their astronomical or symbolic importance, they were more or less well described by the Chinese astronomers, only a part of whose literature has come down to the present day. The asterisms with the brightest stars in the sky were compiled in a work called Shi Shi
. Tianguan is a part of it. Its localisation is made relatively easy by the combination of several factors.
For the majority of asterisms in Shi Shi, the coordinates of a star in the asterism are given, which generally corresponds to the star which is furthest to the West. In the case of asterisms with only one star, it is enough, in principle, to locate the star. The way in which the coordinates are given by the Chinese astronomers have things in common with the equatorial coordinate system
, the equivalent of the longitude
and latitude
on the celestial sphere
, where the poles are determined by the axis of the Earth's rotation, these coordinates are called right ascension
and declination
respectively in astronomy. The Chinese astronomers noted the angular distance of the star, not in relation to the celestial equator, but in relation to the north celestial pole
(which is called the Colatitude
in other contexts), along with the brightness in the right ascension not in relation to a reference point (the equinox
in modern astronomy), but in relation to a set of reference stars of a particular class of asterisms called the twenty-eight mansions
. This kind of measurement was carried out very early for numerous asterisms by Chinese astronomers.
It is possible that the composition of a given asterisms can change over time, although this is very rarely made explicit star by star in astronomical reports. This is more likely to happen when the asterism does not consist of bright stars. But the positioning measures for reference stars were made regularly over time because it seems that the Chinese did not think that the skies were unchangeable. They had observed that the relative positions of the stars were susceptible to change, and that the equatorial coordinate system changed over time due to the slow drift in the direction of the axis of rotation of the Earth. This phenomenon, known since Ancient Greece
, was discovered independently some centuries later by the Chinese under the name of axial precession. In the case of Tianguan, the position of the asterism was reevaluated some months before the arrival of the guest star.
Independent of these new measures, the astronomical reports generally specify the relative position of the asterisms between them. Thus, an asterism is able to be located if its neighbours are robust. In the case of Tianguan, it is indicated that it is located at the foot of the Five Chariots
asterism, the nature of which is left in hardly any doubt by representation on maps of the Chinese sky: it consists of a large pentagon containing the bright stars of the Auriga
. As Tianguan is also represented to the north of the Three Stars
asterism, the composition of which is well known, corresponding to the bright stars of Orion
, its possible localisation is strongly restricted to the immediate proximity of the star ζ Tauri, located between “Five Chariots” and “Three Stars”. This star, of medium brightness (apparent magnitude
of 3.3), is the only star of its level of brightness in this area of the sky (there is no other star that is brighter than an apparent magnitude of 4.5 within 7 degrees of ζ Tauri), and therefore the only one likely to figure among the asterisms of “Shi Shi”. All of these elements, along with some others, allow “Tianguan” to be confirmed beyond doubt as corresponding to the star ζ Tauri.
” reported by the Chinese astronomers correspond to three distinct types of astronomical phenomena: comet
s, nova
s and supernova
s (and more rarely, meteor
s). The distinction between comets and the others is made by observing whether the star in question moves or not. Over the very long period of observation of the guest star of 1054 (642 days, between the 4 July 1054 and the 6 April 1056), there is no mention of movement, and the very long duration of the phenomenon is three times that of the longest reported duration of a comet (just over six months). The guest star is therefore without a shadow of a doubt a nova or a supernova.
The distinction between these two possibilities is made by considering the duration of the phenomenon and its location in the sky. Novae are explosions which occur on the surface of certain stars, from which the curve of light fades very rapidly, rarely lasting longer than a few months. Even though longer novae do exist (one of four guest stars of 1592 is probably an example), they are relatively rare. In addition, novae are less bright phenomena than supernovae. A nova that is visible in the daytime comes from a star that is close to the sun, where the position in the sky is relatively insecure. By contrast, supernovae are a lot more rare, and even though they are visible to the naked eye in our Galaxy
, they are generally a lot further away, in the centre of the spiral arm, meaning that they are seen from Earth in the galactic plane
, in other words, in the bright band which is characteristic of our Galaxy. The guest star of 1054, having a very long period of visibility and being situated on a very weak galactic latitude, presents all the characteristics of a supernova. In order to be able to prove this assertion, what is left of the explosion, meaning the associated supernova remnant
, needs to be found.
The region of ζ Tauri is location in the opposite region to the Galactic Center
. It is there that the depth of the disc of our Milky Way is the shallowest, and therefore the area where there are the least supernovae. In fact, there are only very few identified remnants of supernovas in this area.However, this statement could be biased by the fact that research on remnants of supernovae mainly concentrate in the direction of the galactic center where it is expected that there are more of them; however, the remnants are more easily detectable in the opposite direction to the galactic center, because background emissions are low there, which allows better detection of the remnants with weak surface brightness
. For more information, see the discussion in F. R. Stephenson et D. A. Green's book cited in the reference section, pages 38 to 44. If we centre the research on the star ζ Tauri, there is a remnant located in the immediate proximity: the Crab Nebula
. There is no other remnant within 5 degrees of it. The closest, SNR G180.0-1.7, has a pulsar PSR J0538+2817 in the centre of it, whose characteristic age is hundreds of thousands of years, and the remnant itself has a considerable angular size (3 degrees). Such characteristics indicate an old object.The most precise estimation of the system's age results in its cinematic age, which is tens of thousands of years. The Crab Nebula is the only object which presents the expected characteristics of a young remnant and is therefore considered to the product of the explosion which was observed in 1054.
s, the “South-East” direction thus corresponding to a “bottom-left” location in relation to the reference object (in this case, the star ζ Tauri) when it appears at the South. However, this “South-East” direction has long left modern astronomers perplexed in the context of this event: the logical remnant of the supernova corresponding to the guest star is the Crab Nebula
, but it is not situated to the southeast of ζ Tauri, rather in the opposite direction, to the northwest.
(the degree), but is different for right ascension
(which is expressed in angular hours; an angular hour corresponds to exactly 15 degrees. In Chinese astronomy, right ascension and declination have the same unit, which is not the one used for other angular distances. The reason for this choice to use different units in the Chinese world is not well known.
However, the exact value of these new units (zhang, chi and cun) was never stipulated, but can be deduced by the context in which they are used. For example, the spectacular passing of Halley's comet in 837 indicates that the tail of the comet measured 8 zhang. Even if it is not possible to know the angular size of the comet at the time it passed, it is certain that 8 zhang correspond to 180 degrees at the most (maximum visible angle on the celestial sphere), which means that one zhang can hardly exceed 20 degrees, and therefore one cun cannot exceed 0.2 degrees. A more rigorous estimation was made from 1972 on the basis of references of minimal separations expressed in chi or cun between two stars in the case of various conjunctions. The results suggest that one cun is between 0.1 and 0.2 degrees and that one chi is between 0.44 and 2.8 degrees, a range which is compatible with the estimations for one cun. A more solid estimation error is that it is generally accepted that one chi is in the order of one degree (or one du), and that one cun is in the order of one tenth of a degree. The expression “perhaps a few inches” therefore suggests an angular distance in the order of one degree or less.
In their controversial article (see above) Collins and his colleagues make another suggestion: on the morning of July 4, the star ζ Tauri was not bright enough and too low on the horizon to be visible. If the guest star, which was located close to it, was visible, it is only because its brightness was comparable to Venus. However, there was another star, brighter and higher on the horizon, which was possibly visible, for reference: Beta Tauri
(β Tauri). This star is located at around 8 degrees north-north-west of ζ Tauri. The Crab Nebula is south-south-east of β Tauri. Collins et al. suggest therefore that at the time of its discovery, the star was seen to the south-east of β Tauri, and that as the days passed and visibility improved, astronomers were able to see that it was in fact a lot closer to ζ Tauri, but that the direction “south-east” used for the first star was kept in error.The objective of this demonstration by Collins et al. is not so much to explain the direction problem, but to show that the Chinese observations were not done very seriously. It also seems biased by the presuppositions of these authors.
The solution to this problem was suggested (without proof) by A. Breen and D. McCarthy in 1995. and proved very convincingly by D. A. Green et F. R. StephensonSee work cited in the Reference section. The term “stand on guard” obviously signifies a proximity between the two stars, but also means a general orientation: a guest star “standing on guard” for a fixed star is systematically located below it. In order to support this theory, Green and Stephenson investigated other entries in Song Shi, which also includes reference to “standing on guard”. They selected entries relating to conjunctions betweens the stars identified and planets, of which the trajectory can be calculated without difficulty and with great precision on the indicated dates. Of the 18 conjunctions analysed, spreading from 1172 (the Jupiter
-Regulus
conjunction on 5 December) to 1245 (the Saturn
-Gamma Virginis
conjunction on 17 May), the planet was more to the northIn the sense of a lower declination in 15 cases, and in the three remaining cases, it was never in the south quadrant of the star.
In addition, . F. R. Stephenson and another colleague, David H. Clark had already highlighted such an inversion of direction in a planetary conjunction: on 13 September 1253, an entry in the astronomical report Koryo-sa indicated that Mars
had hidden the star to the south-east of the twenty-eight mansions sign Ghost (Chinese constellation)
(Delta Cancri
), while in reality, it approached the star north-west of the asterism (Eta Cancri
).
In 1921, Carl Otto Lampland was the first to announce that he had seen changes in the structure of the Crab Nebula. This announcement occurred at a time when the nature of the nebulas in the sky was completely unknown. Their nature, size and distance was subject to debate. Observing changes in such objects allows astronomers to determine if their spatial extension is “small” or “large”, in the sense that notable changes in an object as vast as our Milky Way
cannot be seen over a small time period, such a few years, while such changes are possible if the size of the object does not exceed a few light-years.The question of knowing if all of these “clouds” are small objects located in our Galaxy or much larger objects located outside was the object of a set of discussions named The Great Debate
. It was closed by the highlighting of the extragalactic nature of some of these objects, thanks primarily to the observations of Edwin Hubble
. Lampland's comments were confirmed some weeks later by John Charles Duncan, an astronomer at the Mount Wilson Observatory
. He benefitted from photographic material which has not changed since 1909 and in fact made the comparison with older snapshots easy, highlighting a general movement of expansion of the cloud. The points were moving away from the centre, and did so faster as they got further freom the centre.
Also in 1921, Knut Lundmark
compiled the data for the “guest stars” mentioned in the Chinese chronicles known in the West. He based this on older works, having analysed various sources such as the Wenxian Tongkao
, studied for the first time from an astronomical perspective by Jean-Baptiste Biot in the middle of the 19th century. Lundmark gives a list of 60 suspected novae, the generic term for a stellar explosion, in fact covering two defined phenomena, nova
e and supernovae. The nova of 1054, already mentioned by the Biots in 1843,' is part of the list. It stipulates the location of this guest star in a note at the bottom of the page as being “close to NGC 1952”, one of the names for the Crab Nebula, but it does not seem to create an explicit link between them.
In 1928, Edwin Hubble
was the first to note that the changing aspect of the Crab nebula, which was growing bigger in size, suggests that it is the remains of a stellar explosion. He realised that the apparent speed of change in its size signifies that the explosion which it comes from occurred only nine centuries ago, which puts the date of the explosion in the period covered by Lundmark's compilation. He also noted that the only possible nova in the region of the Taurus constellation (where the cloud is located) is that of 1054, whose age is estimated to correspond precisely to an explosion dating from the start of the second millennium.By extrapolating the current expansion of the cloud in the east, we find a date of birth in the course of the 12th century and not in the middle of the 11th century. This apparent dating problem is a result of the fact that the expansion of the cloud is affected by the central pulsar, which tends to accelerates its expansion over time. The average level of expansion of the cloud is thus less than what is currently observed. Hubble therefore deduced, correctly, that this cloud was the remains of the explosion which was observed by Chinese astronomers.
Hubble's comment remains relatively unknown as the physical phenomenon of the explosion was not known at the time. Eleven years later, when the fact that supernovae are very bright phenomena was highlighted by Walter Baade
and Fritz Zwicky
and when their nature was suggested by Zwicky Nicholas Mayall
proposed that the star of 1054 was actually a supernova, based on the speed of expansion of the cloud, measured by spectroscopy, which allows astronomers to determine its physical size and distance, which he estimated at 5000 light-year
s. This was under the assumption that the velocities of expansion along the line of sight and perpendicularly to it were identical. Based on the reference to the brightness of the star which featureD in the first documents discovered in 1934, he deduced that it was a supernova rather than a nova.
This deduction was subsequently refined, which pushed Mayall and Jan Oort
in 1942 to analyse historic accounts relating to the guest star more closely (see section Compilation of Historic Accounts below). These new accounts, globally and mutually concordant, confirm the initial conclusions by Mayall and Oort in 1939 and the identification of the guest star of 1054 is established beyond all reasonable doubt. Most other historical supernovas are not confirmed so conclusively: supernovas of the first millennium (SN 185
, SN 386 and SN 393) are established on the basis of a single document each, and so they cannot be confirmed; in relation to the supposed historical supernova which followed the one in 1054, SN 1181
, there are legitimate doubts concerning the proposed remnant (3C58) and an object of less than 1000 years of age. Other historical supernovae of which there are written accounts which precede the invention of the Telescope
(SN 1006
, SN 1572
and SN 1604
) are however established with certitude.
Its remnant, the Crab Nebula, was one of the first to be discovered in 1731 by John Bevis
.
In 1757, Alexis Clairaut reexamined the calculations of Edmund Halley and precicted the return of Halley's comet in late 1758 (more precisely, he predicted it would pass the perihelion in Spring 1759, with the start of its period of visibility some months earlier).The exact time of the comet's return required the consideration of perturbations to its orbit caused by planets in the Solar System such as Jupiter, which Clairaut and his two colleagues Joseph Jérôme Lefrançois de Lalande and Nicole-Reine Lepaute
carried out more precisely than Halley, finding that the comet should appear in the constellation
of Taurus (constellation)
. It is in searching in vain for the comet that Charles Messier
found the Crab nebula, which he at first thought to be Haley's comet. After some observation, noticing that the object that he was observing was not moving across the sky, Messier concluded that the object was not a comet. Messier then realised the usefulness of compiling a catalogue of celestial objects of a cloudy nature, but fixed in the sky, in order to avoid incorrectly cataloging them as comets.It was Johann Georg Palitzsch
who first observed the return of Halley's comet, in late December 1758.
William Herschel
observed the Crab nebula numerous times between 1783 and 1809, but we do not know whether he was aware of its existence in 1783, or if he discovered it independently of Messier and Bevis. After several observations, he concluded that it was composed of a group of stars.
In 1844, William Parsons
was the first to sketch the cloud, which he named the "Crab Nebula" from 1848. Although the appearance of the drawing is more suggestive of an insect than a crustacean, the epithet "crab" was quickly accepted.
In 1913, when Vesto Slipher
registered his spectroscopy
study of the sky, the Crab nebula was again one of the first objects to be studied. The American astronomer noticed its unique characteristics immediately.
Changes in the cloud, suggesting its small extent, were discovered by Carl Lampland in 1921. That same year, John Charles Duncan demonstrated that the remnant is expanding, while Knut Lundmark
noted its proximity to the guest star of 1054, but did not mention the comments of his two colleagues.
In 1928, Edwin Hubble
proposed associating the cloud to the star of 1054 (see above), an idea which remained confidential until the nature of supernovae was understood, and it was Nicholas Mayall who indicated that the star of 1054 was undoubtedly the supernova whose explosion produced the Crab Nebula. The search for historical supernovae started at that moment: seven other historical sightings have been found by comparing modern observations of supernova remnants with astronomical documents of past centuries. The oldest historical supernova sighting identified, SN 185
, dates from the end of the 2nd century AD.
In the 1960s, due to the prediction and discovery of pulsar
s, the Crab nebula again became a major centre of interest. It was then that Franco Pacini predicted the existence of a neutron star
for the first time, which would explain the brightness of the cloud. This neutron star was observed shortly afterwards in 1968, a shining confirmation of the theory of the formation of these objects at the time of certain supernovae. The discovery of the Crab pulsar, and the knowledge of its exact age (almost to the day) allows for the verification of basic physical properties of these objects, such as characteristic age and spin-down luminosity, the orders of magnitude involved (notably the strength of the magnetic field
), along with various aspects related to the dynamics of the remnant. The particular role of this supernova to the scientific understanding of supernova remnants was crucial, as no other historical supernova created a pulsar whose precise age we can know for certain. The only possible exception to this rule would be SN 1181
whose supposed remnant, 3C58, is home to a pulsar, but its identification using Chinese observations from 1181 is sometimes contested.
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
that was first observed as a new "star" in the sky on July 4, 1054 AD, hence its name, and that lasted for a period of around two years. The event was recorded in multiple Chinese
Sinosphere
In areal linguistics, Sinosphere refers to a grouping of countries and regions that are currently inhabited with a majority of Chinese population or were historically under Chinese cultural influence...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese documents and in one document from the Arab world
Arab world
The Arab world refers to Arabic-speaking states, territories and populations in North Africa, Western Asia and elsewhere.The standard definition of the Arab world comprises the 22 states and territories of the Arab League stretching from the Atlantic Ocean in the west to the Arabian Sea in the...
. While it has been hypothesized that SN 1054 was also observed by American-Indian tribes and Europeans, it has not been conclusively proven.
The remnant
Supernova remnant
A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.There are two...
of SN 1054, which consists of debris ejected during the explosion, is known as the Crab Nebula
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
. It is located in the sky near the star Zeta Tauri
Zeta Tauri
Zeta Tauri is a binary star in the constellation Taurus, the Bull. Known to the ancient Babylonians as Shurnarkabti-sha-shutu, meaning "the star in the bull towards the south," Zeta Tauri is among the most prominent of the stars in well-known constellation figures, representing one of the...
(ζ Tauri). Some of the remnant of the explosion formed a pulsar
Pulsar
A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...
, called the Crab Pulsar
Crab Pulsar
The Crab Pulsar is a relatively young neutron star. The star is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was widely observed on Earth in the year 1054...
(or PSR B0531+21). The nebula and the pulsar it contains are the most studied astronomical objects outside the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
. It is one of the few Galactic
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
supernovae where the date of the explosion is well known. The two objects are the most luminous in their respective categories. For these reasons, and because of the important role it has repeatedly played in the modern era, SN 1054 is the best known supernova in the history of astronomy.
The Crab nebula is easily observed by amateur astronomers thanks to its brightness, and was also catalogued early on by professional astronomers, long before its true nature was understood and identified. When the French astronomer Charles Messier
Charles Messier
Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects"...
watched for the return of Halley's Comet in 1758, he confused the nebula for the comet, as he was unaware of the former's existence. It was because of this error that he created his catalogue of non-cometary nebulous objects, the Messier Catalogue, to avoid such mistakes in the future. The nebula is catalogued as the first Messier object, or M1.
Collection of historical records
SN 1054 is one of eight supernovae that can be identified because written testimony describing the explosion has survived. In the nineteenth century, astronomers began to take an interest in the historic records. They compiled and examined the records as part of their research on recent novaNova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e, comets, and later, the supernovae.
The first people to attempt a systematic compilation of records from China were the father and son Biot. In 1843, the sinologist Édouard Biot
Édouard Biot
Édouard Constant Biot, was a French engineer and Sinologist. As an engineer, he participated in the construction of the second line of French railway between Lyon and St Etienne, and as a Sinologist, published a large body of work, the result of a "knowledge rarely combined.".-Life:Son of the...
translated for his father, the astronomer Jean-Baptiste Biot
Jean-Baptiste Biot
Jean-Baptiste Biot was a French physicist, astronomer, and mathematician who established the reality of meteorites, made an early balloon flight, and studied the polarization of light.- Biography :...
, passages from the astronomical treatise of the 348 volume Chinese encyclopaedia, the Wenxian Tongkao
Wenxian Tongkao
The Wenxian Tongkao or Tongkao was one of the model works of the Tongdian compiled by Ma Duanlin in 1317.-References:*Dong, Enlin, et al. . Historial Literature and Cultural Studies. Wuhan: Hubei Dictionary Press. ISBN 7-5403-0512-6*Xu, Guanglie, . Encyclopedia of China, 1st ed.-External links:* -...
.
Almost 80 years later, in 1921, Knut Lundmark
Knut Lundmark
Knut Emil Lundmark was a Swedish astronomer, professor of astronomy and head of the observatory at Lund University 1929–1955....
undertook a similar effort based on a greater number of sources. In 1942, Jan Oort
Jan Oort
Jan Hendrik Oort was a Dutch astronomer. He was a pioneer in the field of radio astronomy. The Oort cloud of comets bears his name....
, convinced that the Crab Nebula was the "guest star" of 1054 described by the Chinese, asked sinologist Jan Julius Lodewijk Duyvendak, to help him compile new evidence on the observation of the event.
China
Stars which appeared temporarily in the sky were generically called “guest stars” by Chinese astronomers. The guest star of 1054 occurred during the reign of the Emperor RenzongEmperor Renzong of Song
Emperor Renzong was the fourth emperor of the Song Dynasty of China. His personal name was Zhao Zhen . He reigned from 1022 to 1063. Renzong was the son of Emperor Zhenzong of Song. Despite his long reign of over 40 years, Renzong is not widely known...
of the Song dynasty
Song Dynasty
The Song Dynasty was a ruling dynasty in China between 960 and 1279; it succeeded the Five Dynasties and Ten Kingdoms Period, and was followed by the Yuan Dynasty. It was the first government in world history to issue banknotes or paper money, and the first Chinese government to establish a...
(960-1279). The relevant year is recorded in Chinese documents as "the first year of the Zhihe era". "Zhihe" was an era name
Chinese era name
A Chinese era name is the regnal year, reign period, or regnal title used when traditionally numbering years in an emperor's reign and naming certain Chinese rulers . Some emperors have several era names, one after another, where each beginning of a new era resets the numbering of the year back...
used during the reign of Emperor Renzong, and corresponds to the years 1054-1056 C.E., so the first year of the Zhihe era corresponds to the year 1054 C.E.
Six accounts from China relate the observation of the phenomenon. Like almost all of the records relating to the guest star, none of them are first hand: the oldest was about a century after the apparition of the star. Some of these accounts are nevertheless remarkably well preserved, and are used to reconstruct the essential information concerning the observation of the explosion.
Wenxian Tongkao
The Wenxian TongkaoWenxian Tongkao
The Wenxian Tongkao or Tongkao was one of the model works of the Tongdian compiled by Ma Duanlin in 1317.-References:*Dong, Enlin, et al. . Historial Literature and Cultural Studies. Wuhan: Hubei Dictionary Press. ISBN 7-5403-0512-6*Xu, Guanglie, . Encyclopedia of China, 1st ed.-External links:* -...
is the first East Asian source that came to the attention of Western astronomers; it was translated by Édouard Biot in 1843. This source, compiled by Ma Duanlin
Ma Duanlin
Mă Duānlín was a Chinese historical writer and encyclopædist. In 1317 he published the comprehensive Chinese encyclopedia Wenxian Tongkao in 348 volumes....
in 1280, is relatively brief. The text states:
"Tianguan" is the traditional Chinese name for Zeta Tauri
Zeta Tauri
Zeta Tauri is a binary star in the constellation Taurus, the Bull. Known to the ancient Babylonians as Shurnarkabti-sha-shutu, meaning "the star in the bull towards the south," Zeta Tauri is among the most prominent of the stars in well-known constellation figures, representing one of the...
.
Xu Zizhi Tongjian Changbian
The Xu Zizhi Tongjian Changbian ("Long compilation of the continuation of the Zizhi TongjianZizhi Tongjian
The Zizhi Tongjian was a pioneering reference work in Chinese historiography, published in 1084, under the form of a chronicles. In 1065 CE, Emperor Yingzong of Song ordered the great historian Sima Guang to lead with other scholars such as his chief assistants Liu Shu, Liu Ban and Fan Zuyu, the...
"), a book covering the period of 960-1126 and written 40 years or so later by Li Tao (1114–1183), contains the oldest Chinese testimonies relating to the observation of the star. It was rediscovered in 1970 by the specialist in Chinese civilisations Ho Peng Yoke and collaborators.
It is relatively imprecise in the case of the explosion of SN 1054. A loose translation of what was stated :
Song Huiyao
The Song Huiyao (literally "Collected important documents of the Song dynasty") covers the period 960-1220. Huiyao is a traditional form of history books in China which aimed mainly to preserve primary sourcePrimary source
Primary source is a term used in a number of disciplines to describe source material that is closest to the person, information, period, or idea being studied....
s, and as such are important sources supplementing the official Twenty-Four Histories
Twenty-Four Histories
The Twenty-Four Histories is a collection of Chinese historical books covering a period from 3000 BC to the Ming Dynasty in the 17th century. The whole set contains 3213 volumes and about 40 million words...
. The Song dynasty had a specific government department dedicated to compiling the Huiyao, and some 2,200 volumes were published in ten batches during the Song dynasty. However, most of these documents were lost by the time of the Qing Dynasty
Qing Dynasty
The Qing Dynasty was the last dynasty of China, ruling from 1644 to 1912 with a brief, abortive restoration in 1917. It was preceded by the Ming Dynasty and followed by the Republic of China....
except for the synopsis and a relatively small portion preserved as part of the imperial Yongle Encyclopedia
Yongle Encyclopedia
The Yongle Encyclopedia was a Chinese compilation of information commissioned by the Chinese Ming Dynasty emperor Yongle in 1403 and completed by 1408...
. In 1809, the portion preserved in the Yongle Encyclopedia was extracted and re-published as the Song Huiyao Jigao (the "draft extract of the Song Huiyao"). Subsequent scholars have worked on the project further and the current edition dates from 1936.
This document recounts the observation of the guest star, by focusing on the astronomical aspect, but gives more important information relating to the visibility of the star, by day and by night.
Song Shi
The Song Shi is the official annals of the Song dynasty. Chapter 12 mentions the guest star, not its appearance but rather the moment of its disappearance. The corresponding entry dated 6 April 1056 indicates :In chapter 56 ("Astronomical treaty") of the same document, the guest star is again mentioned in a chapter dedicated to this type of phenomenon, this time focusing on its appearance, and this is in terms very close to Wenxian Tongkao :
Qidan Guozhi
There is an account of the star from the Khitan Liao DynastyLiao Dynasty
The Liao Dynasty , also known as the Khitan Empire was an empire in East Asia that ruled over the regions of Manchuria, Mongolia, and parts of northern China proper between 9071125...
, which ruled in the area around Manchuria
Manchuria
Manchuria is a historical name given to a large geographic region in northeast Asia. Depending on the definition of its extent, Manchuria usually falls entirely within the People's Republic of China, or is sometimes divided between China and Russia. The region is commonly referred to as Northeast...
from 907-1125. The book in question, the Qidan Guozhi, was compiled by Ye Longli in 1247. It includes various astronomical notes, some of which are clearly copied from the Song Shi. This entry referring to the star of 1054 seems unique:
Interpretation of Chinese reports
The sky on the morning of 4 July, probable date of the first Chinese observation of the supernova (blue square). The supernova emerged from its conjunction with the Sun, and rose about two hours before it, being observed during part of this period and day.Three of these accounts clearly emanate from the same source: those of Wenxian Tongkao, of Xu Zizhi Tongjian Changbian, and of chapter 56 of Songshi, who had evaluated the angular distance from the star to Tianguan according to the formula "perhaps several inches away". The three documents however are in apparent disagreement about the date of appearance of the star. Two mention the day jichou, and the third, the Xu Zizhi Tongjian Changbian, the day yichou. These terms refer to the Chinese sexagenary cycle, corresponding to numbers 26 and 2 of the cycle, which corresponds, in the context where they are cited, respectively, to July 4 and June 10.
The latter date is considered incorrect for several reasons. On the one hand, the terms yichou and jichou are different from one and other by only one character, the first, and these characters are very similar, yichou and jichou written respectively 乙丑 et 己丑, so a typographical error in re-transcription seems possible. For others, the entries of Xu Zizhi Tongjian Changbian follow a strict chronological order, and previous entries also refer to the Chinese sexagenary cycle, concerning the days yiyou (22) and bingxu (24), while later entries relate to the days yiwei (32, part of the sixth lunar moon), bingshen (33), then renyin (39). In this context, it seems far more likely that the use of yichou is a result of an error in re-transcription rather than a chronological misplacing of the entry. The duration of visibility is explicitly mentioned in chapter 12 of Songshi, and slightly less accurately, in the Song Huiyao, the last sighting was the 6th of April 105613, after a very long period of visibility of 642 days. This duration is supported by the Wenxian Tongkao and chapter 56 of the Songshi. According to the Song Huiyao the visibility of the guest star was for only 23 days, but this is after mentioning visibility during daylight. This period of 23 days applies in all likelihood solely to visibility during the day.
The account of Qidan Guozhi alluded to the notable astronomical events that preceded the death of King Xingzong. Various historical documents allow us to establish the date of death of the Emperor Xingzong as the 28th of August 1055, during the eighth lunar month of the twenty-fourth (and not twenty-third) year of his reign. The dates of the two astronomical events mentioned (the eclipse and the appearance of the guest star) are not specified, but were probably before the obituary (2 or 3 years at most). Two solar eclipses were visible shortly before that date in the Khitan kingdom, on the 13th of November 1053 and the 10th of May 1054. Of these, only one occurred around noon, that of the 13th of November, it seems likely that this is what the document mentions. As for the guest star, only a rough estimate of location is given, corresponding to the moon mansion Mao. This mansion is situated just east of where the star appeared, as mentioned in the other testimonies (see the section General localisation of the Event below). Since no other known significant astronomical event occurred in this region of the sky during the two years that preceded the death of Xingzong, it seems likely that the text is actually referring to the star of 1054.
The location of the guest star can in principle be deducted from the statement “to the south-east of Tianguan, perhaps several inches away “, which for a long time perplexed modern astronomers, because if Tianguan is almost universally regarded as a correspondent for the star Zeta Tauri
Zeta Tauri
Zeta Tauri is a binary star in the constellation Taurus, the Bull. Known to the ancient Babylonians as Shurnarkabti-sha-shutu, meaning "the star in the bull towards the south," Zeta Tauri is among the most prominent of the stars in well-known constellation figures, representing one of the...
(ζ Tauri), the Crab nebula, following a clearly old explosion of stars about 1000 years ago, and therefore a natural candidate for this guest star, is not situated in the south-east but to the north-west of this star (see the General localisation of the Event section below).
Japan
Three texts from Japan mention the guest star. The most detailed of these is that of Meigetsuki. One of the other two, which is less precise, can be taken as his, or at least share a common origin with him. The last record, which is extremely brief, gives very little information.Meigetsuki
Fujiwara no TeikaFujiwara no Teika
Fujiwara no Teika , also known as Fujiwara no Sadaie or Sada-ie, was a Japanese poet, critic, calligrapher, novelist, anthologist, scribe, and scholar of the late Heian and early Kamakura periods...
(1162–1241), a poet and courtier, mentions the guest star of 1054 in his famous diary, the Meigetsuki. Better known for his literary works than for his interest in astronomy, he supplied the most detailed description of the supernova of 1054.
His interest in the guest star seems to have come accidentally whilst observing a comet in December 1230, which prompted him to search for evidence of past guest stars, among those SN 1054 (as well as SN 1006
SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
and SN 1181
SN 1181
First observed between August 4 and August 6, 1181, Chinese and Japanese astronomers recorded the supernova now known as SN 1181 in eight separate texts....
, the two other historic supernovas from the early second millennium). The entry relating to SN 1054 can be translated as:
SN 1054 in Meigetsuki is not a historical record.It was mentioned about relations between the guest stars and ominous incidents,it was a onmyodo superstition.As a result,he concluded that there Are relations between them.
The source used by Fujiwara no Teika is the records of Yasutoshi Abe(Onmyōdō doctor), but it seems to have been based, for all the astronomical events he has recorded, on documents of Japanese origin. The date he gives is prior to the third part of ten days of the lunar month mentioned, which corresponds to the period of between 30 May and the 8th of June 1054 of the Julian calendar, which is around one month earlier than Chinese documentation. This difference is usually attributed to an error in the lunar months (fourth place and fifth place). The location of the guest star, clearly straddling the moon mansions Shen and Zuixi, corresponds to what would be expected of a star appearing in the immediate vicinity of Tianguan.
Ichidai Yoki
Another account exists, taken from Ichidai Yoki, an anonymous document probably compiled during the course of the 14th century. He described the star in a way very similar to the Meigetsuki, omitting several details (hour of apparition, and possibly erroneous parts of the lunar month). The comparison with Jupiter is not present; neither is the possibly incorrect month. In addition, the short text contains many typographical errors, especially involving the second character of Tianguan. Everything suggests that this testimony is from the same source as the Meigetsuki, which could also have been copied.Dainihonshi
Finally, an even shorter text is included in the astronomical treaty of Dainihonshi (litt. “History of Great Japan”). This text can be translated as :« Era of Tengi of the Emperor Go-Reizei, second year, fourth lunar month. A guest star was seen. »
The brevity contrasts with the more detailed descriptions of “guest stars” (actually supernovas) of 1006 and 1181. The reason for the little detail on the entry of 1054 is not known. Like the other two Japanese mentions of the star, it mentions the fourth month and not the fifth.
Interpretation of Japanese reports
Japan's three documents are in agreement as to the month of observation, corresponding to the fourth lunar moon, one month earlier than the Chinese texts. Whatever the exact date during this month, there seems to be a contradiction between this period and the observation of the guest star: the star was in close proximity to the sun, making day time and night time observation impossible. This inconsistency of the dates is further confirmed by a detail in the Meigetsuki : the mention of the double hour chou which corresponds to 1am-3am. This is a long time from sunrise and, since the star and the sun are in close proximity, the star could not possibly rise before the sun.. The Japanese and Chinese testimonies can be reconciled if one considers that there is an error in the month stated in the Japanese observation records. The fact that all the Japanese sources make the same mistake can be interpreted as the fact that they are all from the same source. Doubts as to the month of the observation could have been relieved if the day determined by the Chinese sexagenary cycle had been included, in addition to the observation month, but this is not the case in the Japanese documents. In contrast, the day of the cycle given in the Chinese documents is compatible with the months that they state; reinforcing the idea that the month on the Japanese document is incorrect. For others, the study of other medieval supernovas (SN 1006SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
and SN 1181
SN 1181
First observed between August 4 and August 6, 1181, Chinese and Japanese astronomers recorded the supernova now known as SN 1181 in eight separate texts....
) reveals a close proximity in the dates of discovery of a guest star in China and Japan, although clearly based on different sources. Considering the mention of the fourth lunar month it would then be accurate to imagine that in that event, the Japanese have significantly outperformed their Chinese counterparts, a mystery for which an explanation is not forthcoming.
The Japanese documents do not specify the visibility in daylight, but compare it to Jupiter, which is visible in daylight, and reports of which appear in the astronomical records of the contemporary Chinese world.
The visibility in daylight as described by the Chinese texts is thus validated by the Japanese Documents, and is consistent with a period of moderate visibility, which implies that the star's period of diurnal visibility was very short, even during favourable conditions for observation (a star visible during of sunrise is relatively easy to spot if its position is known and as the background sky becomes more and more luminous).
Korea
No reports of Korean observations of SN 1054 have survived. This has probably because all astronomical records from the year 1054 are missing from the Koryo-sa, the official chronicle relating to this period. It is the same for 1055. In constast, the years 1052 and 1053 contain a large number of entries related to astronomy. The Koryo-sa was compiled in 1451 and it appears likely that, by that time, any document relating to astronomical events observed in 1054 had been lost. No other Korean documents relating to the “guest star” of 1054 have been found since.Arab world
Traditionally, the astronomers of the Arab world were more interested in cyclic and predictable phenomena than those of an unexpected nature such as a “guest star”, perhaps under the influence of Aristotle, who said that the immutability of the heavens, comets and other novae should be considered as weather events rather than astronomy. This would explain the low number of “guest stars”, a term that has no equivalent in medieval Europe or in the Arab world. If SN 1006SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
, which was significantly brighter, was mentioned by several Arab chroniclers, there exist no Arab reports relating to the rather faint SN 1181
SN 1181
First observed between August 4 and August 6, 1181, Chinese and Japanese astronomers recorded the supernova now known as SN 1181 in eight separate texts....
. Only one Arab account has been found concerning SN 1054, whose brightness is between those of the last two stars mentionned. This account, discovered in 1978, is that of a Nestorian Christian doctor, Ibn Butlan
Ibn Butlan
Ibn Butlan was an Iraqi Christian physician of the Islamic Golden Age.He wrote the Taqwim al-Sihhah . The work treated matters of hygiene, dietetics, and exercise. It emphasized the benefits of regular attention to the personal physical and mental well-being...
, transcribed in the Uyun al-Anba, a book compiled by Ibn Abi Usaybi'a (1194–1270) in the mid-thirteenth century. This is the passage in question :
The three years cited (445, 446, 447) refer, respectively, to: 23 April 1053-11 April 1054, 12 April 1054-1 April 1055, and 2 April 1055-20 March 1056. There is an apparent inconsistency in the year of occurrence of the star, first announced as 446, then 445. This problem is solved by reading other entries in the book, which quite explicitly specify that the Nile was low at 446.This year of the Muslim calendar ran from the 12th of April 1054 to the 1st of April 1055, which is compatible with the appearance of the star in July 1054, as its location (admittedly rather vague), is in the astrological sign of Gemini (which, due to Axial precession, covers the eastern part of the Constellation Taurus).The date of the event in 446 is harder to determine, but the reference to the level of the Nile refers to the period preceding its annual flood, which happens during the summer.
Europe
Since the 1980s, several old European documents have been identified as possible observations of the supernova. The relevance of these documents has been criticised, as the dating that they indicate does not correspond to that of the Chinese documents, which they precede by 2 or 3 months, with no mention of any subsequent sightings of the supernova. They are also very imprecise and unconvincing from an astronomical perspective, even when collated. They would also be impossible to interpret in the sense of an observation of a supernova if no information had been preserved from the Chinese accounts.These attempts at linking a genuine celesatial event to very imprecise documents have been strongly criticised by a number of authors, who view them a seeking to promote the existence of sightings of the event in Europe and as being "anxious to ensure that this event was recorded by Europeans". The lack of accounts from European chroniclers has long raised questions. In fact, it is known that supernova of 1006
SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
was recorded in a large number of European documents, albeit not in astronomical terms. Among the proposed explanations for the lack European accounts of SN 1054 is its concurrence with the East-West Schism
East-West Schism
The East–West Schism of 1054, sometimes known as the Great Schism, formally divided the State church of the Roman Empire into Eastern and Western branches, which later became known as the Eastern Orthodox Church and the Roman Catholic Church, respectively...
is prominent. In fact, the date of the excommunication of the Patriarch of Constantinople
Patriarch of Constantinople
The Ecumenical Patriarch is the Archbishop of Constantinople – New Rome – ranking as primus inter pares in the Eastern Orthodox communion, which is seen by followers as the One, Holy, Catholic, and Apostolic Church....
Michael I Cerularius
Michael I Cerularius
Michael I Cerularius , also known as Michael Keroularios or Patriarch Michael I, was the Ecumenical Patriarch of Constantinople from 1043 to 1059.-Biography:...
(16 July) corresponds to the star reaching its maximum brightness and being visible in the daytime. This is only an unverifiable hypothesis, and it is difficult to explain how an account of an event which was visible a priori to everyone could have disappeared without a trace. The fact is however, that European documents of the 11th century were written by people who, despite their extensive learning, possessed extremely limited knowledge of astronomy, and could not even consistently recognise the stars which form various astronomical conjunctions (see examples below).
Jacobus Malvecius' account
The first suggestion of a European account of a sighting of the supernova was made in 1980 by the Italian astronomer Umberto Dall'Olmo (1925–1980). The following passage which reports an astronomical sighting is taken from an account compiled by Jacobus Malvecius in the 15th century:The date that this passage was written is not specified, but in it, there is a reference to an earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
in Brescia
Brescia
Brescia is a city and comune in the region of Lombardy in northern Italy. It is situated at the foot of the Alps, between the Mella and the Naviglio, with a population of around 197,000. It is the second largest city in Lombardy, after the capital, Milan...
, which has been identified as taking place on 11 April 1064. Dall'Olmo did not propose any explanation of this apparent mismatch of ten years between the supernova and the earthquake, besides the hypothesis that it could be the result of a transcription error. Even if this were not the case, the absence of a precise date and position makes the phenomenon difficult to identify, and it could simply be a conjunction
Conjunction (astronomy)
Conjunction is a term used in positional astronomy and astrology. It means that, as seen from some place , two celestial bodies appear near one another in the sky...
between the moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and a planet (probably Venus or Jupiter), or a concealment of a planet by the moon.
The Cronaca Rampona
The account of a supernova sighting which is considered the most feasible comes from a medieval chronicle from the region of BolognaBologna
Bologna is the capital city of Emilia-Romagna, in the Po Valley of Northern Italy. The city lies between the Po River and the Apennine Mountains, more specifically, between the Reno River and the Savena River. Bologna is a lively and cosmopolitan Italian college city, with spectacular history,...
, the Cronaca Rampona. This text, a subject of astronomers' attention since 1972, was interpreted as a possible sighting of the supernova in 1981, and again in 1999. The part of the chronicle that was highlighted indicates that:
“ In the year of Christ Ml8, Pope Stephen IX
Pope Stephen IX
Pope Stephen IX was Pope from August 3, 1057 to March 1058.His baptismal name was Frederick of Lorraine , and he was a younger brother of Godfrey III, Duke of Lower Lorraine, who, as Marquis of Tuscany , played a prominent part in the politics of the period.Frederick, who had...
has come to the throne [...] Also in this year of Christ Ml8, Henry III
Henry III, Holy Roman Emperor
Henry III , called the Black or the Pious, was a member of the Salian Dynasty of Holy Roman Emperors...
reigned [or “ lived ”] for xl9 years. He went to Rome for the first time in the month of May. At this time, famine and death was upon the whole world. He stayed in the province of Tibur
Tivoli
The name Tivoli originally indicates the town of Tivoli in the Lazio region of central Italy, founded a few centuries before Rome. Because of the fame of the gardens of the Villa d'Este there , the name has also been applied to other entities:-Gardens, theatres and venues:* Jardin de Tivoli,...
for three days in the month of June [...] At that moment, a very brightly-shining star entered into the circle [or the circuit] or the new moon, in the thirteenth Calends at the beginning of the night The interesting part of the Latin text says stella clarissima in circuitu prime lune ingressa est, 13 Kalendas in nocte initio
Without even discussing the last, astronomical part of the text, skeptics point out at least two discrepancies in the following : Pope Stephen IX
Pope Stephen IX
Pope Stephen IX was Pope from August 3, 1057 to March 1058.His baptismal name was Frederick of Lorraine , and he was a younger brother of Godfrey III, Duke of Lower Lorraine, who, as Marquis of Tuscany , played a prominent part in the politics of the period.Frederick, who had...
became Pope in 1057, not 1058, and Emperor Henry III who is mentioned, actually Henry III, Holy Roman Emperor
Henry III, Holy Roman Emperor
Henry III , called the Black or the Pious, was a member of the Salian Dynasty of Holy Roman Emperors...
, was born in 1017, 39 and not 49 years before 1058, his reign having started in 1039 (King of the Romans
King of the Romans
King of the Romans was the title used by the ruler of the Holy Roman Empire following his election to the office by the princes of the Kingdom of Germany...
, then as emperor of the Romans from 1046 after being consecrated by Pope Clement II during the course of his brief pontificate). Henry III, therefore, was dead in 1056, and his reign could not have coincided with that of Stephen IX. It seems more likely that the text was the subject of various alterations, as the date format (for example “ Ml8 ” for 1058, the second character of “ Ml8 ” being the lower case letter L), with a mix of Roman (upper and lower case) and Arab characters, was common in the period when the Cronaca Rampona was written (15th century) but not that of the supernova four centuries earlier. Furthermore, associating the event described with the sighting of a supernova in 1054 would require the supposition that the Cronaca Rampona entry was in the wrong place in relation to the rest of the document, as the different entries are in chronological order and several previous entries are later than 1054 ( in order, the previous entries refer to 1046, 1049, 1051, 1055, 1056, written in a mix of Arab and Roman characters, namely Mxl6, Mxl9, Mli, Mlv and Ml6). Additionally, there is a discrepancy with the date of the new moon. The term Calends, which refers to the Roman calendar
Roman calendar
The Roman calendar changed its form several times in the time between the founding of Rome and the fall of the Roman Empire. This article generally discusses the early Roman or pre-Julian calendars...
, can be written in the ordinary form of the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...
, and the phase of the moon can be calculated from it. It is clear that the new moon did not occur on the thirteenth day of the Calends in any month in 1054.Historically, the Kalendes were based on the phases of the Moon, the start of a Kalende corresponded with a new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...
. Par la suite un décalage s'opéra avec la phase de la Lune, mais la position de celle-ci varie lentement d'une Kalende à l'autre. So no month from December 1050 to May 1056 had a new moon fall on the 13th of the month. All of this is in strong opposition to the precision of the dates of references to eclipses in medieval European chronicles : a study of 48 partial or total solar eclipse
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...
s from 733 to 1544, reveals that 42 dates out of 48 are correct, and of the six remaining, three are incorrect by one of two days and the three others give the correct day and month, but not the year. Finally, even considering that the stated event corresponds to May or June 1054 nevertheless, and describes a conjunction between the already visible supernova and the moon, another problem arises : during those months, the moon did not pass very close to the location of the supernova. Incidentally, the vocabulary used in the Latin text is somewhat unusual. The Latin word translated into English as circle is circuitu, used in place of the more commonly used circulus, but this semantic variant does not seem to change the sense of the text, which, in all possible translations of circuitu, suggests an object which is found on or close to the moon's path of travel.
Therefore, it is possible that the account describes an approach or a concealment of a planet by the moon, contemporary to the suggested date (1058). This scenario is corroborated by two contemporary documents which are perfectly dated and describe a conjunction and a planetary concealment by the moon in relatively similar terms. These two documents, unearthed by Robert Russell Newton
Robert Russell Newton
Robert Russell Newton, also R. R. Newton was an American physicist, astronomer, and historian of science.Newton was Supervisor of the Applied Physics Laboratory at Johns Hopkins University. Newton was known for his book The Crime of Claudius Ptolemy . In Newton's view, Ptolemy was "the most...
, are taken from the Annales Cavenses, Latin chronicles from la Trinità della Cava
La Trinità della Cava
La Trinità della Cava is a Benedictine abbey located near Cava de' Tirreni, in the province of Salerno, southern Italy. It stands in a gorge of the Finestre Hills.-History:...
(Province of Salerno
Province of Salerno
The Province of Salerno is a province in the Campania region of Italy.-Geography:The largest towns in the province are: Salerno, the capital, which has a population of 139,579; Cava de' Tirreni with a population of 53,488; Battipaglia with a population of 51,115; and Nocera Inferiore which has a...
, Southern Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
). They mention a “bright star that entered into the circle of the new moon” [Martii incipiente nocte] stella clarissima in circulum lunae primae ingressa est for 17 February 1086 and stella clarissima venit in circulum lunae for 6 August. on dates corresponding to 17 February 1086 and 6 August 1096. Calculations indicate that Venus was eclipsed by the moon for half an hour on the 17th February. On the 6th August, Jupiter passed to less than one degree from the moon after a lunar eclipse
Lunar eclipse
A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...
which was also mentioned in the chronicle. The fact that the chronicler or chroniclers did not realise that they had seen a planet rather than a new star demonstrates the weak astronomical knowledge of the scholars of the time, whose astronomical accounts are actually very difficult to interpret and attribute to a rare event.
The Church of Oudenburg's account
In 1992, a group of Italians proposed a Flemish text as an account of a sighting of the supernova. The text, from Saint Paul's church—no longer existent—in the FlemishFlanders
Flanders is the community of the Flemings but also one of the institutions in Belgium, and a geographical region located in parts of present-day Belgium, France and the Netherlands. "Flanders" can also refer to the northern part of Belgium that contains Brussels, Bruges, Ghent and Antwerp...
town of Oudenberg, describes the death of Pope Leo IX
Pope Leo IX
Pope Saint Leo IX , born Bruno of Eguisheim-Dagsburg, was Pope from February 12, 1049 to his death. He was a German aristocrat and as well as being Pope was a powerful secular ruler of central Italy. He is regarded as a saint by the Roman Catholic Church, with the feast day of April 19...
in Spring 1054.
The date described corresponds to the 14th April 1054, the “ second day of the week ” being a Monday, according to the custom of the time. This simple date causes several problems : numerous historical documents describing the death of the Pope state the date as the 19th April and not the 14th. Additionally, neither of these days were Mondays. The astronomical part of the text is also difficult to interpret and associate with the supernova. The description of the phenomenon, which is difficult to identify, is very brief, which contrasts with the timescale of a supernova. Il is not given a location in the sky and the time of the sighting is not given, not even whether it was during the day or the night. There are a priori numerous optical or atmospheric phenomena which can impress a chronicler who is not a specialist in astronomy, such as aurora
Aurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
s (at night) or a solar halo
Halo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
(in the daytime). Most importantly, the reference to “ everywhere on earth ” could correspond to a non-localised event, but it is not possible to know the exact meaning of such a reference.
Albertus' account
In a work entitled De Obitus Leonis, the author, Libuinus, reported an unusual celestial phenomenon which was seen on the day that Leo IX died by a group of pilgrims lead by a certain Albertus, who were in the region of TodiTodi
Todi is a town and comune of the province of Perugia in central Italy. It is perched on a tall two-crested hill overlooking the east bank of the river Tiber, commanding distant views in every direction.In the 1990s, Richard S...
(Umbria
Umbria
Umbria is a region of modern central Italy. It is one of the smallest Italian regions and the only peninsular region that is landlocked.Its capital is Perugia.Assisi and Norcia are historical towns associated with St. Francis of Assisi, and St...
north of Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...
). He seems to have confirmed seeing :
The nature of the observed phenomenon is difficult to identify, as the subject is enshrouded in mystery. Certain authors have proposed that he actually described the supernova. A favourable moment would have been at dusk, when the sun was setting before the star ζ Tauri. However, on that night, a concentration of planets was in that area of the sky : Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
, Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
, Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
, and Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
slightly further away. That area of the sky is also rich in bright stars (the constellation of Orion
Orion (constellation)
Orion, often referred to as The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky...
, Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...
, Capella
Capella
Capella can refer to:* Capella , a bright star in the constellation of Auriga* Capella , an impact crater on the Moon* Capella, Queensland, a small town in Central Queensland* Capella Island, a minor island of the U.S...
etc.), and it is possible that these, along with the planets, formed the “ countless lamps ” in Albertus' account. Considering this vast concentration of brightness, the supernova's presence would not have been remarkable. Just like the preceding account, this text directly links the death of the Pope to an “ extraordinary ” event, which could have been done to justify a miracle associated with the deceased, in order to facilitate his canonisation (which was carried out by Pope Victor III
Pope Victor III
Pope Blessed Victor III , born Daufer , Latinised Dauferius, was the Pope as the successor of Pope Gregory VII, yet his pontificate is far less impressive in history than his time as Desiderius, the great Abbot of Monte Cassino.-Early life and abbacy:He was born in 1026 or 1027 of a non-regnant...
in 1087).
Reference in an Armenian chronicle
In 1969, two Armenian authors published a list of accounts of meteor sightings from ArmeniaArmenia
Armenia , officially the Republic of Armenia , is a landlocked mountainous country in the Caucasus region of Eurasia...
n chronicles. One of the authors stated some years later that one of the documents could correspond to a sighting of the supernova of 1054. According to his translation of the document, it indicates :
This brief description strongly suggests a closening or concealment of a planet or bright star by the moon. In fact, calculations indicate that on the date mentioned, the moon got closer by around 3 degrees, when Cancer
Cancer (constellation)
Cancer is one of the twelve constellations of the zodiac. Its name is Latin for crab and it is commonly represented as such. Its symbol is . Cancer is small and its stars are faint...
was in conjunction with Jupiter, a fact which the theorists advocating a sighting of the supernova failed to verify or even mention.This conjunction is not in the article of Collins et al., which actually claims to have calculated the event as occurring on the night of 11th May 1054.
Summary of the European documents
Among the six European documents, one does not seem to correspond to the year of the supernova (the chronicle of Jacobus Malvecius). Another (the Cronaca Rampona) has large dating and internal coherence problems. The four others are relatively precisely dated, but contradict the Chinese documents : they date from Spring and not Summer 1054, that is to say before the conjunction between the supernova and the sun. Three of the documents (the chronicle of Jacobus Malvecius, the Cronaca Rampona and the Armenian chronicle) make reference relatively explicitly to conjunctions between the moon and stars, of which one is identified (Jupiter, in the Armenian chronicle). Calculations indicate that the moon never got significantly close to the supernova in Spring 1054. The three other documents are very unclear and have almost unusable astronomical content, if it is even real. None of the documented phenomena lasted very long (half an hour in the Church of Oudenberg's account, five hours in the Irish annals and an undetermined, but explicitly short, duration in Albertus' account). No document stipulates the region of the sky where the phenomena took place, and there were no indications as to when the sightings occurred. Supposing the phenomena described have a real physical base, numerous atmospheric phenomena could be the cause.In a more general manner, these documents are not actually astronomical, but produced by learned chroniclers who had limited astronomical knowledge. This is evident in the most workable document, the Armenian chronicle, where the usual conjunction between the moon and Jupiter is not recognised as such, as is the case for numerous other conjunctions.For example those in the aforementioned Annales Cavenses.
A reinterpretation of the European sightings
In 1999, George W. CollinsGeorge W. Collins
George Washington Collins was a Democratic member of the U.S. House of Representatives from Illinois.Collins was born in Chicago, and served with the Army engineers in the South Pacific during World War II...
and his colleagues proposed a radical reinterpretation of the European documents and claimed that they convincingly indicate that the Europeans had seen the supernova well before Chinese astronomers.
Concerning the Chinese documents, they point out their various date errors (see above) as proof that the quality of their observations was inferior to what is commonly accepted, and therefore that nothing rules out the possibility that more hardened observers may have seen the supernova beforehand. They also make their point by bringing up the problem of the localisation of the supernova in relation to the star ζ Tauri (see below). Finally, based on a controversial translation of the document from khitan people, they claim that the supernova was probably visible at the time of the solar eclipse of 10 May 1054.
In the opposite way, they reinterpret the European documents as relatively corroborating in relation to the fact that a notable astronomical event occurred in Spring 1054, before the conjunction between the supernova and the sun. They believe that the metaphoric aspect of certain documents only reflects the observers' limited knowledge of the sky, without prejudicing their ability to observe., Furthermore, they claim that the date problems in the Cronoca Rampona are not errors, as the European chroniclers are not interested in being very precise concerning dates. They also mention, without further elaboration, that the Chinese observations of guest stars was primarily of an astrological, and not scientific, nature, which could make their content biased.
As for the reference to the supernova in d'Ibn Butlan scripture, they trust the date of 445 in the Muslim calendar (23 April 1053 — 11 April 1054) and not 446 (12 April 1054 — 1 April 1055) to confirm that the supernova was visible from April 1054, without taking into account the fact that other parts of the scripture are more coherent with the date of 446, not 445.
The works of Collins et al. were strongly criticised by F. Richard Stephenson
F. Richard Stephenson
Professor F. Richard Stephenson is an Emeritus Professor at the Physics department and East Asian Studies department at the University of Durham. His research concentrates on historical aspects of astronomy, for example analysing ancient astronomical records. He has an asteroid named after him...
and David A. Green, who pointed out a lack of seriousness in the analysis of their colleagues. Notably, they insist that date problems in Asian documents are easily resolved. One of them (the Xu Zizhi Tongjian Changbian) corresponds in a relatively obvious way to a typographic error, and the other (the month of observation of Japanese documents) to a common date error in this set of documents. They mention that claiming that the supernova was visible at the time of the solar eclipse on May 10, 1054 is based on an inappropriate interpretation of the translation and is contrary to astronomical reality. In fact, this eclipse having only been partial, no star close to the sun could have been seen at that time. Finally, they insist on the lack of astronomical knowledge of the European chroniclers compared to the Chinese atronomers. According to them, this point makes it difficult to attribute these documents to an observation of the supernova. If this was the case, it would be necessary to explain why no European document mentions the supernova in Summer, when it was perfectly visible according to the Chinese documents, and how the more experienced Chinese and Japanese observers could have missed the supernova at this time. They also note that even in the case of a concordance of dates, nothing proves that events which occurred in the same year correspond to a single astronomical phenomenon. The guest stars of 837 are an example of two different novas which occurred in the same year (additionally marked by the spectacular passing of Halley's comet). The four guest stars of 1592 reinforce this comment. Green and Stephenson's conclusions add to previous works dating from 1995 where the different European observations had already been rejected due to their lack of precision and the impossibility to draw clear astronomical sense from them.
The thesis of Collins et al. was not broadly taken up in scientific literature afterwards,The ADS
Astrophysics Data System
The Astrophysics Data System , developed by the National Aeronautics and Space Administration , is an online database of over eight million astronomy and physics papers from both peer reviewed and non-peer reviewed sources...
database only includes three articles that cite this reference: (list) but has nevertheless enjoyed a certain visibility to the general public, notably being taken up by the magazine Ciel & Espace with a certain enthusiasm.
North America
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
paintings in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
show a crescent moon located next to a circle that could represent a star. It has been proposed that this represents a conjunction between the moon and the supernova, made possible by the fact that, seen from the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, the supernova occurred in the path of the Ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
.
This theory is compatible with the datings in these paintings. In fact, on the morning of 5 July, the moon was located in the immediate proximity of the supernova, which could reinforce the idea that it was this proximity that had been represented in these paintings. This interpretation cannot be confirmed. The dating of the paintings is extremely imprecise (between the 10th and 12th century), and only one of them shows the crescent moon with the correct orientation in relation to the supernova. Moreover, this type of drawing could well represent a proximity of the moon with Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
or Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
.
Another, better known document was updated during the 1970s at the Chaco Canyon
Chaco Culture National Historical Park
Chaco Culture National Historical Park is a United States National Historical Park hosting the densest and most exceptional concentration of pueblos in the American Southwest. The park is located in northwestern New Mexico, between Albuquerque and Farmington, in a remote canyon cut by the Chaco Wash...
site (New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
), occupied around 1000 AD by the Anasazi
Ancient Pueblo Peoples
Ancient Pueblo People or Ancestral Pueblo peoples were an ancient Native American culture centered on the present-day Four Corners area of the United States, comprising southern Utah, northern Arizona, northwest New Mexico, and southern Colorado...
. On a vertical surface plane of a construction, it represents a hand, below which there is a crescent moon facing a star at the bottom-left. On the ground in front of the petroglyph there is a drawing which could be the core and tail of a comet. Apart from the petroglyph, which could represent the configuration of the moon and supernova on the morning of 5 July 1054, this period corresponds to the apogee of the Anasazi civilisation. It seems possible to propose an interpretation of the other petroglyph, which, if it is more recent than the other one, could possibly correspond to the passing of Halley's Comet in 1066. Although plausible, this interpretation is impossible to confirm and does not explain why it was the supernova of 1054 that was represented, rather than the supernova of 1006
SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
, which was brighter and also visible to this civilisation.
Location
The most precise indications of the localisation of the event make reference to a Chinese constellationChinese constellation
Chinese constellations are the way the ancient Chinese grouped the stars. They are very different from the modern IAU recognized constellations. This is because the IAU was based on Greco-Roman astronomy instead of Chinese astronomy....
(asterism
Asterism (astronomy)
In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one. Like constellations, asterisms are in most cases composed of stars which, while they are visible in the same general direction,...
in Western astronomical science) called Tianguan by Chinese astronomers.
The constellations (asterisms) of Chinese astronomy are generally smaller than the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
s of the western world, and some of these named "asterisms" can consist of a single star. They were catalogued around the 2nd century BC. Depending on the brightness of the stars and their astronomical or symbolic importance, they were more or less well described by the Chinese astronomers, only a part of whose literature has come down to the present day. The asterisms with the brightest stars in the sky were compiled in a work called Shi Shi
Shi Shi
Shi Shi was briefly the emperor of the Jie/Chinese Hun state Later Zhao following his father Shi Hu's death in 349. In the Chinese annals he is sometimes referred to by his title after removal as an Emperor, Prince of Qiao .Shi Shi was Shi Hu's youngest son, by his third empress Empress Liu,...
. Tianguan is a part of it. Its localisation is made relatively easy by the combination of several factors.
For the majority of asterisms in Shi Shi, the coordinates of a star in the asterism are given, which generally corresponds to the star which is furthest to the West. In the case of asterisms with only one star, it is enough, in principle, to locate the star. The way in which the coordinates are given by the Chinese astronomers have things in common with the equatorial coordinate system
Equatorial coordinate system
The equatorial coordinate system is a widely-used method of mapping celestial objects. It functions by projecting the Earth's geographic poles and equator onto the celestial sphere. The projection of the Earth's equator onto the celestial sphere is called the celestial equator...
, the equivalent of the longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
and latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
on the celestial sphere
Celestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...
, where the poles are determined by the axis of the Earth's rotation, these coordinates are called right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
and declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
respectively in astronomy. The Chinese astronomers noted the angular distance of the star, not in relation to the celestial equator, but in relation to the north celestial pole
Celestial pole
The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere...
(which is called the Colatitude
Colatitude
In spherical coordinates, colatitude is the complementary angle of the latitude, i.e. the difference between 90° and the latitude.-Astronomical use:The colatitude is useful in astronomy because it refers to the zenith distance of the celestial poles...
in other contexts), along with the brightness in the right ascension not in relation to a reference point (the equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...
in modern astronomy), but in relation to a set of reference stars of a particular class of asterisms called the twenty-eight mansions
Twenty-eight mansions
The Twenty-eight Mansions , ', ' or ' are part of the Chinese constellations system. They can be considered as the equivalent to the zodiacal constellations in the Western astronomy, though the Twenty-eight Mansions reflect the movement of the Moon in a lunar month rather than the Sun in a solar year...
. This kind of measurement was carried out very early for numerous asterisms by Chinese astronomers.
It is possible that the composition of a given asterisms can change over time, although this is very rarely made explicit star by star in astronomical reports. This is more likely to happen when the asterism does not consist of bright stars. But the positioning measures for reference stars were made regularly over time because it seems that the Chinese did not think that the skies were unchangeable. They had observed that the relative positions of the stars were susceptible to change, and that the equatorial coordinate system changed over time due to the slow drift in the direction of the axis of rotation of the Earth. This phenomenon, known since Ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
, was discovered independently some centuries later by the Chinese under the name of axial precession. In the case of Tianguan, the position of the asterism was reevaluated some months before the arrival of the guest star.
Independent of these new measures, the astronomical reports generally specify the relative position of the asterisms between them. Thus, an asterism is able to be located if its neighbours are robust. In the case of Tianguan, it is indicated that it is located at the foot of the Five Chariots
Five Chariots
Five Chariots is a constellation in Chinese astronomy.-Introduction:A five-star Chinese constellation that contains Auriga plus Beta Tauri. Also known as Gosha.-Stars:* Iota Aurigae* Alpha Aurigae* Beta Aurigae...
asterism, the nature of which is left in hardly any doubt by representation on maps of the Chinese sky: it consists of a large pentagon containing the bright stars of the Auriga
Auriga (constellation)
Auriga is a constellation in the northern sky. Its name is Latin for 'charioteer' and its stars form a shape that has been associated with the pointed helmet of a charioteer. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains among the 88 modern...
. As Tianguan is also represented to the north of the Three Stars
Three Stars (Chinese constellation)
The Three Stars mansion is one of the twenty-eight mansions of the Chinese constellations. It is one of the western mansions of the White Tiger. This collection of seven bright stars is visible during winter in the Northern Hemisphere .- Asterisms :...
asterism, the composition of which is well known, corresponding to the bright stars of Orion
Orion (constellation)
Orion, often referred to as The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky...
, its possible localisation is strongly restricted to the immediate proximity of the star ζ Tauri, located between “Five Chariots” and “Three Stars”. This star, of medium brightness (apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of 3.3), is the only star of its level of brightness in this area of the sky (there is no other star that is brighter than an apparent magnitude of 4.5 within 7 degrees of ζ Tauri), and therefore the only one likely to figure among the asterisms of “Shi Shi”. All of these elements, along with some others, allow “Tianguan” to be confirmed beyond doubt as corresponding to the star ζ Tauri.
Comet, nova or supernova?
“Guest starsGuest star (astronomy)
In Chinese astronomy, the term guest star refers to a star which has suddenly appeared visible in the place where no star had previously been observed and becomes invisible again after some time. The term is a literal translation from ancient Chinese astronomical records...
” reported by the Chinese astronomers correspond to three distinct types of astronomical phenomena: comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s, nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
s and supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
s (and more rarely, meteor
METEOR
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...
s). The distinction between comets and the others is made by observing whether the star in question moves or not. Over the very long period of observation of the guest star of 1054 (642 days, between the 4 July 1054 and the 6 April 1056), there is no mention of movement, and the very long duration of the phenomenon is three times that of the longest reported duration of a comet (just over six months). The guest star is therefore without a shadow of a doubt a nova or a supernova.
The distinction between these two possibilities is made by considering the duration of the phenomenon and its location in the sky. Novae are explosions which occur on the surface of certain stars, from which the curve of light fades very rapidly, rarely lasting longer than a few months. Even though longer novae do exist (one of four guest stars of 1592 is probably an example), they are relatively rare. In addition, novae are less bright phenomena than supernovae. A nova that is visible in the daytime comes from a star that is close to the sun, where the position in the sky is relatively insecure. By contrast, supernovae are a lot more rare, and even though they are visible to the naked eye in our Galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
, they are generally a lot further away, in the centre of the spiral arm, meaning that they are seen from Earth in the galactic plane
Galactic plane
The galactic plane is the plane in which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles...
, in other words, in the bright band which is characteristic of our Galaxy. The guest star of 1054, having a very long period of visibility and being situated on a very weak galactic latitude, presents all the characteristics of a supernova. In order to be able to prove this assertion, what is left of the explosion, meaning the associated supernova remnant
Supernova remnant
A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.There are two...
, needs to be found.
The region of ζ Tauri is location in the opposite region to the Galactic Center
Galactic Center
The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 8.33±0.35 kpc from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest...
. It is there that the depth of the disc of our Milky Way is the shallowest, and therefore the area where there are the least supernovae. In fact, there are only very few identified remnants of supernovas in this area.However, this statement could be biased by the fact that research on remnants of supernovae mainly concentrate in the direction of the galactic center where it is expected that there are more of them; however, the remnants are more easily detectable in the opposite direction to the galactic center, because background emissions are low there, which allows better detection of the remnants with weak surface brightness
Surface brightness
The overall brightness of an extended astronomical object such as a galaxy, star cluster, or nebula, can be measured by its total magnitude, integrated magnitude or integrated visual magnitude; a related concept is surface brightness, which specifies the brightness of a standard-sized piece of an...
. For more information, see the discussion in F. R. Stephenson et D. A. Green's book cited in the reference section, pages 38 to 44. If we centre the research on the star ζ Tauri, there is a remnant located in the immediate proximity: the Crab Nebula
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
. There is no other remnant within 5 degrees of it. The closest, SNR G180.0-1.7, has a pulsar PSR J0538+2817 in the centre of it, whose characteristic age is hundreds of thousands of years, and the remnant itself has a considerable angular size (3 degrees). Such characteristics indicate an old object.The most precise estimation of the system's age results in its cinematic age, which is tens of thousands of years. The Crab Nebula is the only object which presents the expected characteristics of a young remnant and is therefore considered to the product of the explosion which was observed in 1054.
The Problem of the Precise Localisation of the Residue
Three Chinese documents indicate that the guest star was located “perhaps a few inches” South-East of Tianguan. Song Shi and Song Huiyao stipulate that it “was standing guard” for the asterism, corresponding to the star ζ Tauri. The “South-East”orientation has a simple astronomical meaning, the celestial sphere having, like the Earth's globe, both north and south celestial poleCelestial pole
The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere...
s, the “South-East” direction thus corresponding to a “bottom-left” location in relation to the reference object (in this case, the star ζ Tauri) when it appears at the South. However, this “South-East” direction has long left modern astronomers perplexed in the context of this event: the logical remnant of the supernova corresponding to the guest star is the Crab Nebula
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
, but it is not situated to the southeast of ζ Tauri, rather in the opposite direction, to the northwest.
Angular distance
The term “perhaps a few inches” (ke chi cun in the Latin transliteration) is relatively uncommon in Chinese astronomical documents. The first term, ke, is translated as “approximately” or “perhaps”, the latter being currently preferred. The second term, chi, means “several”, and more specifically any number between 3 and 9 (limits included). Finally, cun resembles a unit of measurement for angles translated by the term “inch”. It is part of a group of three angular units, zhang (also written chang), chi (“foot”) and cun (“inch”). Different astronomical documents indicate without much possible discussion that a zhang corresponds to ten chi, and that one chi corresponds to ten cun. The angular units are not the ones used to determine stars' coordinates, which are given in terms of du, an angular unit corresponding to the average angular distance travelled by then sun per day, which corresponds to around 360/365.25 degrees, in other words barely one degree. The use of different angular units can be surprising, but it is hardly different to the current situation in modern astronomy, where the angular unit used to measure angular distances between two points is certainly the same as for declinationDeclination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
(the degree), but is different for right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
(which is expressed in angular hours; an angular hour corresponds to exactly 15 degrees. In Chinese astronomy, right ascension and declination have the same unit, which is not the one used for other angular distances. The reason for this choice to use different units in the Chinese world is not well known.
However, the exact value of these new units (zhang, chi and cun) was never stipulated, but can be deduced by the context in which they are used. For example, the spectacular passing of Halley's comet in 837 indicates that the tail of the comet measured 8 zhang. Even if it is not possible to know the angular size of the comet at the time it passed, it is certain that 8 zhang correspond to 180 degrees at the most (maximum visible angle on the celestial sphere), which means that one zhang can hardly exceed 20 degrees, and therefore one cun cannot exceed 0.2 degrees. A more rigorous estimation was made from 1972 on the basis of references of minimal separations expressed in chi or cun between two stars in the case of various conjunctions. The results suggest that one cun is between 0.1 and 0.2 degrees and that one chi is between 0.44 and 2.8 degrees, a range which is compatible with the estimations for one cun. A more solid estimation error is that it is generally accepted that one chi is in the order of one degree (or one du), and that one cun is in the order of one tenth of a degree. The expression “perhaps a few inches” therefore suggests an angular distance in the order of one degree or less.
The direction
If all the available elements strongly suggest that the star of 1054 was a supernova, and that in the area next to where the star was seen, there is a remnant of a supernova which has all of the characteristics expected of an object that is around 1000 years old, a major problem arises: the new star is described as being to the South-East of Tianguan, while the Crab Nebula is to the North-East. This problem has been known since the 1940s and has long been unsolved. In 1972 for example, Ho Peng Yoke and his colleagues suggested that the Crab Nebula was not the product of the explosion of 1054, but that the true remnant was to the South-East, as indicated in several Chinese sources. For this, they envisaged that the angular unit cun corresponds to a considerable angle of 1 or 2 degrees, meaning that the distance from the remnant to ζ Tauri was therefore considerable. Aside from the fact that this theory does not account for the large angular sizes of certain comets, expressed in zhang, it comes up against the fact that there it does not make sense to measure the gap between a guest star and a star located so far away from it, when there are closer asterisms that could be used.In their controversial article (see above) Collins and his colleagues make another suggestion: on the morning of July 4, the star ζ Tauri was not bright enough and too low on the horizon to be visible. If the guest star, which was located close to it, was visible, it is only because its brightness was comparable to Venus. However, there was another star, brighter and higher on the horizon, which was possibly visible, for reference: Beta Tauri
Beta Tauri
Beta Tauri is the second brightest star in the constellation Taurus, with an apparent magnitude of 1.68. Because it is on the boundary of Taurus and Auriga, it also has the redundant Bayer designation Gamma Aurigae , which today is rarely used...
(β Tauri). This star is located at around 8 degrees north-north-west of ζ Tauri. The Crab Nebula is south-south-east of β Tauri. Collins et al. suggest therefore that at the time of its discovery, the star was seen to the south-east of β Tauri, and that as the days passed and visibility improved, astronomers were able to see that it was in fact a lot closer to ζ Tauri, but that the direction “south-east” used for the first star was kept in error.The objective of this demonstration by Collins et al. is not so much to explain the direction problem, but to show that the Chinese observations were not done very seriously. It also seems biased by the presuppositions of these authors.
The solution to this problem was suggested (without proof) by A. Breen and D. McCarthy in 1995. and proved very convincingly by D. A. Green et F. R. StephensonSee work cited in the Reference section. The term “stand on guard” obviously signifies a proximity between the two stars, but also means a general orientation: a guest star “standing on guard” for a fixed star is systematically located below it. In order to support this theory, Green and Stephenson investigated other entries in Song Shi, which also includes reference to “standing on guard”. They selected entries relating to conjunctions betweens the stars identified and planets, of which the trajectory can be calculated without difficulty and with great precision on the indicated dates. Of the 18 conjunctions analysed, spreading from 1172 (the Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
-Regulus
Regulus
Regulus is the brightest star in the constellation Leo and one of the brightest stars in the night sky, lying approximately 77.5 light years from Earth. Regulus is a multiple star system composed of four stars which are organized into two pairs...
conjunction on 5 December) to 1245 (the Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
-Gamma Virginis
Gamma Virginis
Gamma Virginis is a star in the constellation Virgo. It has the traditional names Porrima, Postvarta and Arich....
conjunction on 17 May), the planet was more to the northIn the sense of a lower declination in 15 cases, and in the three remaining cases, it was never in the south quadrant of the star.
In addition, . F. R. Stephenson and another colleague, David H. Clark had already highlighted such an inversion of direction in a planetary conjunction: on 13 September 1253, an entry in the astronomical report Koryo-sa indicated that Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
had hidden the star to the south-east of the twenty-eight mansions sign Ghost (Chinese constellation)
Ghost (Chinese constellation)
The Ghost mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the southern mansions of the Vermilion Bird.-Asterisms:...
(Delta Cancri
Delta Cancri
Delta Cancri is an orange giant star approximately 180 light-years away in the constellation Cancer. It has the traditional name Asellus Australis which in Latin means "southern donkey colt"...
), while in reality, it approached the star north-west of the asterism (Eta Cancri
Eta Cancri
Eta Cancri is a star in the constellation Cancer.η Cancri is an orange K-type giant with an apparent magnitude of +5.33. It is approximately 312 light years from Earth....
).
Modern identification of the supernova
In modern times, the star of 1054 was identified as a supernova between the 1920s and the 1940s.In 1921, Carl Otto Lampland was the first to announce that he had seen changes in the structure of the Crab Nebula. This announcement occurred at a time when the nature of the nebulas in the sky was completely unknown. Their nature, size and distance was subject to debate. Observing changes in such objects allows astronomers to determine if their spatial extension is “small” or “large”, in the sense that notable changes in an object as vast as our Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
cannot be seen over a small time period, such a few years, while such changes are possible if the size of the object does not exceed a few light-years.The question of knowing if all of these “clouds” are small objects located in our Galaxy or much larger objects located outside was the object of a set of discussions named The Great Debate
The Great Debate
In astronomy, the Great Debate, also called the Shapley–Curtis Debate, was an influential debate between the astronomers Harlow Shapley and Heber Curtis which concerned the nature of spiral nebulae and the size of the universe...
. It was closed by the highlighting of the extragalactic nature of some of these objects, thanks primarily to the observations of Edwin Hubble
Edwin Hubble
Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
. Lampland's comments were confirmed some weeks later by John Charles Duncan, an astronomer at the Mount Wilson Observatory
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...
. He benefitted from photographic material which has not changed since 1909 and in fact made the comparison with older snapshots easy, highlighting a general movement of expansion of the cloud. The points were moving away from the centre, and did so faster as they got further freom the centre.
Also in 1921, Knut Lundmark
Knut Lundmark
Knut Emil Lundmark was a Swedish astronomer, professor of astronomy and head of the observatory at Lund University 1929–1955....
compiled the data for the “guest stars” mentioned in the Chinese chronicles known in the West. He based this on older works, having analysed various sources such as the Wenxian Tongkao
Wenxian Tongkao
The Wenxian Tongkao or Tongkao was one of the model works of the Tongdian compiled by Ma Duanlin in 1317.-References:*Dong, Enlin, et al. . Historial Literature and Cultural Studies. Wuhan: Hubei Dictionary Press. ISBN 7-5403-0512-6*Xu, Guanglie, . Encyclopedia of China, 1st ed.-External links:* -...
, studied for the first time from an astronomical perspective by Jean-Baptiste Biot in the middle of the 19th century. Lundmark gives a list of 60 suspected novae, the generic term for a stellar explosion, in fact covering two defined phenomena, nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e and supernovae. The nova of 1054, already mentioned by the Biots in 1843,' is part of the list. It stipulates the location of this guest star in a note at the bottom of the page as being “close to NGC 1952”, one of the names for the Crab Nebula, but it does not seem to create an explicit link between them.
In 1928, Edwin Hubble
Edwin Hubble
Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
was the first to note that the changing aspect of the Crab nebula, which was growing bigger in size, suggests that it is the remains of a stellar explosion. He realised that the apparent speed of change in its size signifies that the explosion which it comes from occurred only nine centuries ago, which puts the date of the explosion in the period covered by Lundmark's compilation. He also noted that the only possible nova in the region of the Taurus constellation (where the cloud is located) is that of 1054, whose age is estimated to correspond precisely to an explosion dating from the start of the second millennium.By extrapolating the current expansion of the cloud in the east, we find a date of birth in the course of the 12th century and not in the middle of the 11th century. This apparent dating problem is a result of the fact that the expansion of the cloud is affected by the central pulsar, which tends to accelerates its expansion over time. The average level of expansion of the cloud is thus less than what is currently observed. Hubble therefore deduced, correctly, that this cloud was the remains of the explosion which was observed by Chinese astronomers.
Hubble's comment remains relatively unknown as the physical phenomenon of the explosion was not known at the time. Eleven years later, when the fact that supernovae are very bright phenomena was highlighted by Walter Baade
Walter Baade
Wilhelm Heinrich Walter Baade was a German astronomer who worked in the USA from 1931 to 1959.-Biography:He took advantage of wartime blackout conditions during World War II, which reduced light pollution at Mount Wilson Observatory, to resolve stars in the center of the Andromeda galaxy for the...
and Fritz Zwicky
Fritz Zwicky
Fritz Zwicky was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy.- Biography :Fritz Zwicky was born in Varna, Bulgaria to a Swiss father....
and when their nature was suggested by Zwicky Nicholas Mayall
Nicholas Mayall
Nicholas Ulrich Mayall was an American observational astronomer. After obtaining his doctorate from the University of California, Berkeley, Mayall worked at the Lick Observatory, where he remained from 1934–1960, except for a brief period at MIT's Radiation Laboratory during World War II.During...
proposed that the star of 1054 was actually a supernova, based on the speed of expansion of the cloud, measured by spectroscopy, which allows astronomers to determine its physical size and distance, which he estimated at 5000 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s. This was under the assumption that the velocities of expansion along the line of sight and perpendicularly to it were identical. Based on the reference to the brightness of the star which featureD in the first documents discovered in 1934, he deduced that it was a supernova rather than a nova.
This deduction was subsequently refined, which pushed Mayall and Jan Oort
Jan Oort
Jan Hendrik Oort was a Dutch astronomer. He was a pioneer in the field of radio astronomy. The Oort cloud of comets bears his name....
in 1942 to analyse historic accounts relating to the guest star more closely (see section Compilation of Historic Accounts below). These new accounts, globally and mutually concordant, confirm the initial conclusions by Mayall and Oort in 1939 and the identification of the guest star of 1054 is established beyond all reasonable doubt. Most other historical supernovas are not confirmed so conclusively: supernovas of the first millennium (SN 185
SN 185
SN 185 was a supernova which appeared in the year 185 AD, near the direction of Alpha Centauri, between the constellations Circinus and Centaurus, centered at RA Dec , in Circinus. This "guest star" was observed by Chinese astronomers in the Book of Later Han, and may have been recorded in Roman...
, SN 386 and SN 393) are established on the basis of a single document each, and so they cannot be confirmed; in relation to the supposed historical supernova which followed the one in 1054, SN 1181
SN 1181
First observed between August 4 and August 6, 1181, Chinese and Japanese astronomers recorded the supernova now known as SN 1181 in eight separate texts....
, there are legitimate doubts concerning the proposed remnant (3C58) and an object of less than 1000 years of age. Other historical supernovae of which there are written accounts which precede the invention of the Telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
(SN 1006
SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
, SN 1572
SN 1572
SN 1572 , "B Cassiopeiae" , or 3C 10 was a supernova of Type Ia in the constellation Cassiopeia, one of about eight supernovae visible to the naked eye in historical records...
and SN 1604
SN 1604
Supernova 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a supernova that occurred in the Milky Way, in the constellation Ophiuchus. , it is the last supernova to have been unquestionably observed in our own galaxy, occurring no farther than 6 kiloparsecs or about...
) are however established with certitude.
Importance in the development of modern astronomy
SN 1054 has been involved several times, sometimes fortuitously, in the history of astronomy.Most events in this section were presented in Nicholas Mayall's article, published in 1939.Its remnant, the Crab Nebula, was one of the first to be discovered in 1731 by John Bevis
John Bevis
John Bevis was an English doctor and astronomer. He is best known for discovering the Crab Nebula in 1731....
.
In 1757, Alexis Clairaut reexamined the calculations of Edmund Halley and precicted the return of Halley's comet in late 1758 (more precisely, he predicted it would pass the perihelion in Spring 1759, with the start of its period of visibility some months earlier).The exact time of the comet's return required the consideration of perturbations to its orbit caused by planets in the Solar System such as Jupiter, which Clairaut and his two colleagues Joseph Jérôme Lefrançois de Lalande and Nicole-Reine Lepaute
Nicole-Reine Lepaute
Nicole-Reine Lepaute, née Étable , was a French astronomer and mathematician. She predicted the return of Halley's Comet, calculated the timing of a solar eclipse and constructed a group of catalogs for the stars...
carried out more precisely than Halley, finding that the comet should appear in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Taurus (constellation)
Taurus (constellation)
Taurus is one of the constellations of the zodiac. Its name is a Latin word meaning 'bull', and its astrological symbol is a stylized bull's head:...
. It is in searching in vain for the comet that Charles Messier
Charles Messier
Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects"...
found the Crab nebula, which he at first thought to be Haley's comet. After some observation, noticing that the object that he was observing was not moving across the sky, Messier concluded that the object was not a comet. Messier then realised the usefulness of compiling a catalogue of celestial objects of a cloudy nature, but fixed in the sky, in order to avoid incorrectly cataloging them as comets.It was Johann Georg Palitzsch
Johann Georg Palitzsch
Johann Georg Palitzsch was a German astronomer who became famous for recovering Comet 1P/Halley on Christmas Day, 1758...
who first observed the return of Halley's comet, in late December 1758.
William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...
observed the Crab nebula numerous times between 1783 and 1809, but we do not know whether he was aware of its existence in 1783, or if he discovered it independently of Messier and Bevis. After several observations, he concluded that it was composed of a group of stars.
In 1844, William Parsons
William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse, Knight of the Order of St Patrick was an Irish astronomer who had several telescopes built. His 72-inch telescope "Leviathan", built 1845, was the world's largest telescope until the early 20th century.-Life:He was born in Yorkshire, England, in the city of...
was the first to sketch the cloud, which he named the "Crab Nebula" from 1848. Although the appearance of the drawing is more suggestive of an insect than a crustacean, the epithet "crab" was quickly accepted.
In 1913, when Vesto Slipher
Vesto Slipher
Vesto Melvin Slipher was an American astronomer. His brother Earl C. Slipher was also an astronomer and a director at the Lowell Observatory....
registered his spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
study of the sky, the Crab nebula was again one of the first objects to be studied. The American astronomer noticed its unique characteristics immediately.
Changes in the cloud, suggesting its small extent, were discovered by Carl Lampland in 1921. That same year, John Charles Duncan demonstrated that the remnant is expanding, while Knut Lundmark
Knut Lundmark
Knut Emil Lundmark was a Swedish astronomer, professor of astronomy and head of the observatory at Lund University 1929–1955....
noted its proximity to the guest star of 1054, but did not mention the comments of his two colleagues.
In 1928, Edwin Hubble
Edwin Hubble
Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
proposed associating the cloud to the star of 1054 (see above), an idea which remained confidential until the nature of supernovae was understood, and it was Nicholas Mayall who indicated that the star of 1054 was undoubtedly the supernova whose explosion produced the Crab Nebula. The search for historical supernovae started at that moment: seven other historical sightings have been found by comparing modern observations of supernova remnants with astronomical documents of past centuries. The oldest historical supernova sighting identified, SN 185
SN 185
SN 185 was a supernova which appeared in the year 185 AD, near the direction of Alpha Centauri, between the constellations Circinus and Centaurus, centered at RA Dec , in Circinus. This "guest star" was observed by Chinese astronomers in the Book of Later Han, and may have been recorded in Roman...
, dates from the end of the 2nd century AD.
In the 1960s, due to the prediction and discovery of pulsar
Pulsar
A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...
s, the Crab nebula again became a major centre of interest. It was then that Franco Pacini predicted the existence of a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
for the first time, which would explain the brightness of the cloud. This neutron star was observed shortly afterwards in 1968, a shining confirmation of the theory of the formation of these objects at the time of certain supernovae. The discovery of the Crab pulsar, and the knowledge of its exact age (almost to the day) allows for the verification of basic physical properties of these objects, such as characteristic age and spin-down luminosity, the orders of magnitude involved (notably the strength of the magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
), along with various aspects related to the dynamics of the remnant. The particular role of this supernova to the scientific understanding of supernova remnants was crucial, as no other historical supernova created a pulsar whose precise age we can know for certain. The only possible exception to this rule would be SN 1181
SN 1181
First observed between August 4 and August 6, 1181, Chinese and Japanese astronomers recorded the supernova now known as SN 1181 in eight separate texts....
whose supposed remnant, 3C58, is home to a pulsar, but its identification using Chinese observations from 1181 is sometimes contested.