Comet Arend-Roland
Encyclopedia
Comet Arend–Roland was discovered on November 8, 1956, by Belgian astronomers Sylvain Arend and Georges Roland on photographic plates. As the eighth comet
found in 1956, it was named Arend–Roland 1956h after its discoverers. Because it was the third comet to pass through perihelion during 1957, it was then renamed 1957 III. Finally, it received the standard IAU
designation C/1956 R1 (Arend–Roland), with the 'C/' indicating it was a non-periodic comet and the R1 showing it was the first comet reported as discovered in the half-month designated by R. The last is equivalent to the period September 1–15.
was being used for routine investigation of minor planet
s. On November 8, 1956, the Belgian astronomers Sylvain Arend and Georges Roland discovered a comet on their photographic plates. At that time the comet was at visual magnitude 10, with a strong central condensation and a short tail. The early discovery of this comet allowed observing programs and equipment to be prepared well in advance.
The orbital elements for this comet were computed by Michael P. Candy, who predicted perihelion passage on April 8, 1957. As the comet was already well developed, he predicted that the object would present a prominent display during the month of April in the northern hemisphere. In early December the comet was 2.5 AU
from the Sun and 1.7 AU from the Earth. It was in the constellation
Pisces until February, when it reached magnitude 7.5–8.
During the April perihelion passage, the tail of the comet reached a length of 15° of arc. The appearance of the tail varied, with streamers on April 16 and May 5, and the tail splitting into three beams on the 29th. By April 22 the comet also displayed a prominent anomalous tail (or antitail
) spanning 5°. This antitail stretched out to span 12° on April 25, reaching its maximum extent. The antitail had disappeared by April 29.
Following perihelion, the comet began to fade rapidly. At the start of May it was measured at visual magnitude 5.46. By the eighth it had decreased to magnitude 7, well below the sensitivity limit of the unaided human eye. On May 29 it had dropped to magnitude 8.55.
This was the first comet that attempts were made to detect it at various radio frequencies. However, these efforts were unsuccessful. A comet would not be successfully detected in the radio band until the 1973 passage of comet Kohoutek
.
Comet Arend–Roland was the subject of the very first edition of the BBC's long running astronomy program The Sky at Night
on April 24, 1957.
Astronomer Carl Sagan
relates an anecdote on page 80 of his book Cosmos
about being on duty in an observatory near Chicago in 1957 when a late night phone call from an inebriated man asked what was the "fuzzy thing" they were seeing in the sky. Sagan told the man it was a comet (Arend–Roland). The man asked what a comet was, and Sagan answered that it was "a snowball, one mile wide". After a long pause, the man said, quoting Sagan: "Lemme talk to a real 'shtronomer!".
orbit, meaning it is traveling fast enough to escape from the solar system entirely, hence implying it will never be seen again by earthbound observers. Observations of the comet over a period of 520 days allowed precise orbital elements to be computed. However, the distribution of the orbital elements showed a wavy pattern that suggested a non-gravitational influence. Alternatively, the comet may have originated from interstellar space rather than from the Oort cloud
. When an orbital solution is computed that includes non-gravitational forces that vary as the inverse square of the heliocentric distance, somewhat different values are derived. (See the Marsden (1970) column in the table below.)
At perihelion, the comet was emitting an estimated of dust and was releasing roughly gas molecules. It is believed that an outburst of dust occurred on April 2, six days before perihelion. The antitail was formed from particles released between February 6 and March 1, 1957. Estimates of the total amount of dust released into the zodiac
al cloud range from to .
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...
found in 1956, it was named Arend–Roland 1956h after its discoverers. Because it was the third comet to pass through perihelion during 1957, it was then renamed 1957 III. Finally, it received the standard IAU
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
designation C/1956 R1 (Arend–Roland), with the 'C/' indicating it was a non-periodic comet and the R1 showing it was the first comet reported as discovered in the half-month designated by R. The last is equivalent to the period September 1–15.
Observations
In November 1956, a double astrograph at the Uccle Observatory in BrusselsBrussels
Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...
was being used for routine investigation of minor planet
Minor planet
An asteroid group or minor-planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid...
s. On November 8, 1956, the Belgian astronomers Sylvain Arend and Georges Roland discovered a comet on their photographic plates. At that time the comet was at visual magnitude 10, with a strong central condensation and a short tail. The early discovery of this comet allowed observing programs and equipment to be prepared well in advance.
The orbital elements for this comet were computed by Michael P. Candy, who predicted perihelion passage on April 8, 1957. As the comet was already well developed, he predicted that the object would present a prominent display during the month of April in the northern hemisphere. In early December the comet was 2.5 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from the Sun and 1.7 AU from the Earth. It was 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....
Pisces until February, when it reached magnitude 7.5–8.
During the April perihelion passage, the tail of the comet reached a length of 15° of arc. The appearance of the tail varied, with streamers on April 16 and May 5, and the tail splitting into three beams on the 29th. By April 22 the comet also displayed a prominent anomalous tail (or antitail
Antitail
An Antitail is a term used in astronomy to describe one of the three tails, all pointing in different directions, which may appear to emanate from a comet as it passes close to the Sun. The antitail appears, when viewed from Earth, as a spike projecting from the comet's coma towards the sun, and...
) spanning 5°. This antitail stretched out to span 12° on April 25, reaching its maximum extent. The antitail had disappeared by April 29.
Following perihelion, the comet began to fade rapidly. At the start of May it was measured at visual magnitude 5.46. By the eighth it had decreased to magnitude 7, well below the sensitivity limit of the unaided human eye. On May 29 it had dropped to magnitude 8.55.
This was the first comet that attempts were made to detect it at various radio frequencies. However, these efforts were unsuccessful. A comet would not be successfully detected in the radio band until the 1973 passage of comet Kohoutek
Comet Kohoutek
Comet Kohoutek, formally designated C/1973 E1, 1973 XII, and 1973f, was first sighted on 7 March 1973 by Czech astronomer Luboš Kohoutek. It attained perihelion on 28 December that same year....
.
Comet Arend–Roland was the subject of the very first edition of the BBC's long running astronomy program The Sky at Night
The Sky at Night
The Sky at Night is a monthly documentary television programme on astronomy produced by the BBC. The show has had the same permanent presenter, Sir Patrick Moore, from its first airing on 24 April 1957, making it the longest-running programme with the same presenter in television history.The...
on April 24, 1957.
Astronomer Carl Sagan
Carl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...
relates an anecdote on page 80 of his book Cosmos
Cosmos
In the general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος , meaning "order" or "ornament" and is antithetical to the concept of chaos. Today, the word is generally used as a synonym of the word Universe . The word cosmos originates from the same root...
about being on duty in an observatory near Chicago in 1957 when a late night phone call from an inebriated man asked what was the "fuzzy thing" they were seeing in the sky. Sagan told the man it was a comet (Arend–Roland). The man asked what a comet was, and Sagan answered that it was "a snowball, one mile wide". After a long pause, the man said, quoting Sagan: "Lemme talk to a real 'shtronomer!".
Properties
It was traveling on a hyperbolicHyperbola
In mathematics a hyperbola is a curve, specifically a smooth curve that lies in a plane, which can be defined either by its geometric properties or by the kinds of equations for which it is the solution set. A hyperbola has two pieces, called connected components or branches, which are mirror...
orbit, meaning it is traveling fast enough to escape from the solar system entirely, hence implying it will never be seen again by earthbound observers. Observations of the comet over a period of 520 days allowed precise orbital elements to be computed. However, the distribution of the orbital elements showed a wavy pattern that suggested a non-gravitational influence. Alternatively, the comet may have originated from interstellar space rather than from the Oort cloud
Oort cloud
The Oort cloud , or the Öpik–Oort cloud , is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun...
. When an orbital solution is computed that includes non-gravitational forces that vary as the inverse square of the heliocentric distance, somewhat different values are derived. (See the Marsden (1970) column in the table below.)
| Orbital Element | Sekanina (1968) | Marsden (1970) |
|---|---|---|
| Epoch of periastron Apsis An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system... (T) |
1957 April 8.03232 ET | 1957 April 8.03201 ET |
| Perihelion distance (q) | 0.3160540 ± 0.0000008 AU | 0.3160361 ± 0.0000024 AU |
| Inverse semi-major axis Semi-major axis The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape... (1/a) |
–0.0007886 ± 0.0000045 AU−1 | –0.0006377 ± 0.0000213 AU−1 |
| Eccentricity Orbital eccentricity The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit... (e) |
1.0002492 ± 0.0000014 | 1.0002015 ± 0.0000067 |
| Inclination Inclination Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit... (i) |
119.94936° ± 0.00005° | 119.94930° ± 0.00006° |
| Longitude of periastron Longitude of the periapsis In astrodynamics, the longitude of the periapsis of an orbiting body is the longitude at which the periapsis would occur if the body's inclination were zero. For motion of a planet around the sun, this position could be called longitude of perihelion... (ω) |
307.78084° ± 0.00004° | 308.77725° ± 0.00048° |
| Position angle Position angle Position angle, usually abbreviated PA, is a measurement derived from observing visual binary stars. It is defined as the angular offset in degrees of the secondary star to the primary, relative to the north celestial pole.... of the ascending node Orbital node An orbital node is one of the two points where an orbit crosses a plane of reference to which it is inclined. An orbit which is contained in the plane of reference has no nodes.-Planes of reference:... (Ω) |
215.15900° ± 0.00006° | 215.15968° ± 0.00008° |
At perihelion, the comet was emitting an estimated of dust and was releasing roughly gas molecules. It is believed that an outburst of dust occurred on April 2, six days before perihelion. The antitail was formed from particles released between February 6 and March 1, 1957. Estimates of the total amount of dust released into the zodiac
Zodiac
In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...
al cloud range from to .
External links
- Orbital simulation from JPL (Java) / Ephemeris
- C/1956 R1 (Arend–Roland)
- Picture of Antitail