Occultation - AbsoluteAstronomy.com

An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy

Astronomy

Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

(see below). It can also refer to any situation wherein an object in the foreground blocks from view (occult

Occult

The word occult comes from the Latin word occultus , referring to "knowledge of the hidden". In the medical sense it is used to refer to a structure or process that is hidden, e.g...

s) an object in the background. In this general sense, occultation applies to the visual scene observed from low-flying aircraft (or computer-generated imagery

Computer-generated imagery

Computer-generated imagery is the application of the field of computer graphics or, more specifically, 3D computer graphics to special effects in art, video games, films, television programs, commercials, simulators and simulation generally, and printed media...

) wherein foreground objects obscure distant dynamically, as the scene changes over time.

Occultations, transits and eclipses

An occultation occurs when an apparently larger body passes in front of an apparently smaller one. A transit occurs when an apparently smaller body passes in front of an apparently larger one. In the combined case where the smaller body regularly transits

Astronomical transit

The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...

the larger object, an occultation is also termed a secondary eclipse.

An eclipse occurs when a body disappears or partially disappears from view, either by an occultation, as with a 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...

, or by passing into the shadow of another body, as with 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...

(thus both are listed on NASA's eclipse page).

Transits, occultations and eclipses in general are all effects of a syzygy

Syzygy (astronomy)

In astronomy, a syzygy is a straight line configuration of three celestial bodies in a gravitational system. The word is usually used in reference to the Sun, the Earth and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of...

.

Transits and occultations of the sun by Earth's moon are called solar eclipse

Solar eclipse

s regardless of whether the sun is completely or partially covered. By extension, transits of the sun by a satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

of a planet may also be called eclipses, as with the transits of Phobos and Deimos shown here, as may the passage of a satellite into the planet's shadow, as with this eclipse of Phobos. The term eclipse is also used more generally for bodies passing in front of one another. For example, this entry from NASA's Astronomy Picture of the Day refers to the Moon eclipsing and occulting Saturn interchangeably.

Occultations by the Moon

The term occultation is most frequently used to describe those relatively frequent occasions when 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...

passes in front of a star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

during the course of its orbital motion around the Earth. Since the Moon, with an angular speed with respect to the stars of 0.55 arcsec/s or 2.7 µrad/s, has no atmosphere and stars have an angular diameter of at most 0.057 arcseconds or 0.28 µrad, a star that is occulted by the moon will disappear or reappear in 0.1 seconds or less on the moon's edge, or limb. Events that take place on the Moon's dark limb are of particular interest to observers, because the lack of glare allows these occultations to more easily be observed and timed.

The Moon's orbit is inclined to 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...

(see orbit of the Moon), and any stars with an ecliptic latitude of less than about 6.5 degrees may be occulted by it. There are three first magnitude stars that are sufficiently close to the ecliptic that they may be occulted by the Moon and by planets – 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...

, Spica

Spica

Spica is the brightest star in the constellation Virgo, and the 15th brightest star in the nighttime sky. It is 260 light years distant from Earth...

and Antares

Antares

Antares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky . Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic...

. Occultations of Aldebaran

Aldebaran

Aldebaran is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky...

are presently only possible by the Moon, because the planets pass Aldebaran to the north. Neither planetary nor lunar occultations of Pollux

Pollux (star)

Pollux is an orange giant star approximately 34 light-years from the Earth in the constellation of Gemini . Pollux is the brightest star in the constellation, brighter than Castor...

are currently possible. However, in the far future, occultations of Aldebaran and Pollux will be possible, as they were in the far past. Some deep-sky objects, such as the Pleiades

Pleiades (star cluster)

In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...

, can also be occulted by the moon.

Within a few kilometres of the edge of an occultation's predicted path, referred to as its northern or southern limit, an observer may see the star intermittently disappearing and reappearing as the irregular limb of the Moon moves past the star, creating what is known as a Grazing lunar occultation

Grazing lunar occultation

A lunar occultation occurs when the Moon, moving along its orbital path, passes in front of a star or other celestial object, as seen by an observer...

. From an observational and scientific standpoint, these "grazes" are the most dynamic and interesting of lunar occultations.

The accurate timing of lunar occultations is performed regularly by (primarily amateur) astronomers. Lunar occultations timed to an accuracy of a few tenths of a second have various scientific uses, particularly in refining our knowledge of lunar topography. Photoelectric analysis of lunar occultations have also discovered some stars to be very close visual or spectroscopic binaries

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

. Some angular diameters of stars have been measured by timing of lunar occultations, which is useful for determining effective temperature

Effective temperature

The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation...

s of those stars. Early radio astronomers found occultations of radio sources by the Moon valuable for determining their exact positions, because the long wavelength of radio waves limited the resolution available through direct observation. This was crucial for the unambiguous identification of the radio source 3C 273 with the optical quasar and its jet, and a fundamental prerequisite for Maarten Schmidt

Maarten Schmidt

Maarten Schmidt is a Dutch astronomer who measured the distances of quasars.Born in Groningen, The Netherlands, Schmidt studied with Jan Hendrik Oort. He earned his Ph.D. degree from Leiden Observatory in 1956....

's discovery of the cosmological nature of quasars.

Several times during the year, someone on Earth can usually observe the Moon occulting a planet. Since planets, unlike stars, have significant angular sizes, lunar occultations of planets will create a narrow zone on earth from which a partial occultation of the planet will occur. An observer located within that narrow zone could observe the planet's disk partly blocked by the slowly moving moon.

Occultation by planets

Stars may also be occulted by planets. In 1959, 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...

occulted Regulus

Regulus

. Uranus

Uranus

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

' rings were first discovered when that planet occulted a star in 1977. On the evening of July 2-July 3, 1989, 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,...

passed in front of the 5th magnitude star 28 Sagittarii

Sagittarius (constellation)

Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...

. Pluto, which was re-designated as a dwarf planet in 2006, occulted stars in 1988, 2002, and 2006, allowing its tenuous atmosphere to be studied.

It is also possible for one planet to occult another planet. However, these mutual occultations of planets are extremely rare. The last such event occurred on January 3, 1818 and will next occur on November 22, 2065, in both cases involving the same two planets—Venus and Jupiter. Technically speaking, when the foreground planet is smaller in apparent size than the background planet, the event should be called a "mutual planetary transit." When the foreground planet is larger in apparent size than the background planet, the event should be called a "mutual planetary occultation." (See Transit

Astronomical transit

for a list of past and future events).

Twice during the orbital cycles of Jupiter and Saturn, the equatorial (and satellite) planes of those planets are aligned with earth's orbital plane, resulting in a series of mutual occultations and eclipses between the moons of these giant planets. These orbital alignments have also occurred artificially when unmanned spacecraft have traversed these planetary systems, resulting in photographs such as the one shown here. The terms "eclipse," "occultation" and "transit" are also used to describe these events. A satellite of Jupiter (for example) may be eclipsed (i.e. made dimmer because it moves into Jupiter's shadow), occulted (i.e. hidden from view because Jupiter lies on our line of sight), or may transit (i.e. pass in front of) Jupiter's disk.

Occultations by asteroids

An asteroid occultation occurs when an asteroid

Asteroid

Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

(also known as a 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...

) passes in front of a star

Star

(occults a star), temporarily blocking its light (as seen from 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...

). Several events occur nearly every day over the world. From any particular place such events occur almost every night, although most require a 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...

to see.

Asteroid occultations are useful for measuring the size and position of asteroids much more precisely than can be done by any other means. A cross-sectional profile of the shape of an asteroid can even be determined if a number of observers at different, nearby, locations observe the occultation. For example, on March 12, 2009 there were 8 minor planet occulations, including (85) Io, (247) Eukrate, (1585) Union, (201) Penelope, (70) Panopaea, (980) Anacostia, (2448) Sholokhov, (1746) Brouwer, and (191) Kolga. Any one of these would be expected to occult at a time and place on the globe, at a certain magnitude, and with a certain star.

For example, according to the 1998 European Asteroidal Occultation Results from Euraster, 39 Laetitia was observed by over 38 observatories in one occultation on March 3, 1998, which resulted in many chords being determined.

Occultations have produced outlines of many asteroids. Some notable ones include:

Name	Chords	Measured Profile (km)
704 Interamnia 704 Interamnia 704 Interamnia is a very large asteroid, with an estimated diameter of 350 kilometres. Its mean distance from the Sun is 3.067 . It was discovered on October 2, 1910 by Vincenzo Cerulli, and named after the Latin name for Teramo, Italy, where Cerulli worked...	35	350×304
39 Laetitia 39 Laetitia 39 Laetitia is a large, bright main-belt asteroid.Laetitia was discovered by J. Chacornac on February 8, 1856, and named after Laetitia, a minor Roman goddess of gaiety....	~16	219×142
94 Aurora 94 Aurora 94 Aurora is one of the largest main-belt asteroids. With an albedo of only 0.04, it is darker than soot, and has a primitive compositions consisting of carbonaecous material. It was discovered by J. C...	9	225×173
375 Ursula 375 Ursula 375 Ursula is one of the largest asteroids from the asteroid belt. It was discovered by Auguste Charlois on September 18, 1893, in Nice.Observations of an occultation on November 15, 1984, produced six chords indicating an estimated diameter of 216±10 km.-External links:* from JPL /...	6	216±10
444 Gyptis 444 Gyptis 444 Gyptis is a very large main-belt asteroid. It is classified as a C-type asteroid and is probably composed of carbonaceous material.It was discovered by J...	6	179×150
48 Doris 48 Doris 48 Doris is one of the largest main belt asteroids. It was discovered by Hermann Goldschmidt on September 19, 1857 from his balcony in Paris.-Name:...	4	278×142

Occultations have also been used to estimate the diameter of trans-Neptunian object

Trans-Neptunian object

A trans-Neptunian object is any minor planet in the Solar System that orbits the Sun at a greater distance on average than Neptune.The first trans-Neptunian object to be discovered was Pluto in 1930...

s such as (55636) 2002 TX300

(55636) 2002 TX300

is a bright Kuiper belt object in the outer Solar System estimated to be about 286 km in diameter. It is a large member of the Haumea family, discovered on October 15, 2002, by the Near-Earth Asteroid Tracking program....

, 28978 Ixion

28978 Ixion

28978 Ixion is a Kuiper belt object discovered on May 22, 2001. Ixion is a plutino and a very likely dwarf planet; its diameter of 650 km estimated by Spitzer makes it about the fifth largest plutino. It is named after Ixion, a figure from Greek mythology...

, and 20000 Varuna

20000 Varuna

20000 Varuna is a large classical Kuiper belt object and a probable dwarf planet. It previously had the provisional designation ' and has been precovered in plates dating back to 1953.-Name:Varuna is named after the Hindu deity,...

. Preliminary results of a 6 November 2010 occultation by the dwarf planet Eris

Eris (dwarf planet)

Eris, formal designation 136199 Eris, is the most massive known dwarf planet in the Solar System and the ninth most massive body known to orbit the Sun directly...

of a 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...

17 star 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 Cetus

Cetus

Cetus is a constellation. Its name refers to Cetus, a sea monster in Greek mythology, although it is often called 'the whale' today. Cetus is located in the region of the sky that contains other water-related constellations such as Aquarius, Pisces, and Eridanus.-Ecliptic:Although Cetus is not...

placed an upper limit on Eris's diameter of 2320 km, making it almost the same size as Pluto. Due to their slower movement through the night sky, occultations by TNOs are far less common than by asteroids in the main-belt.

Double occultations

It is possible that the moon or another celestial body can occult multiple celestial bodies at the same time. Such events are extremely rare and can be seen only from a small part of the world. The last event of such type was on April 23, 1998 when the moon occulted Venus and Jupiter simultaneously for observers on Ascension Island

Ascension Island

Ascension Island is an isolated volcanic island in the equatorial waters of the South Atlantic Ocean, around from the coast of Africa and from the coast of South America, which is roughly midway between the horn of South America and Africa...

Occulting satellites

The Big Occulting Steerable Satellite (BOSS) was a proposed satellite

Satellite

that would work in conjunction with a telescope

Telescope

to detect planet

Planet

A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

s around distant stars. The satellite consists of a large, very lightweight sheet, and a set of maneuvering thrusters and navigation systems. It would maneuver to a position along the line of sight between the telescope and a nearby star. The satellite would thereby block the radiation from the star, permitting the orbiting planets to be observed.

The proposed satellite would have a dimension of 70 m × 70 m, a mass of about 600 kg, and maneuver by means of an ion drive engine in combination with using the sheet as a light sail. Positioned at a distance of 100,000 km from the telescope, it would block more than 99.998% of the starlight.

There are two possible configurations of this satellite. The first would work with a space telescope, most likely positioned near 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...

's Lagrangian point

Lagrangian point

The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

. The second would place the satellite in a highly elliptical orbit about the Earth, and work in conjunction with a ground telescope. At the apogee of the orbit, the satellite would remain relatively stationary with respect to the ground, allowing longer exposure times.

An updated version of this design is called the Starshade, which uses a sunflower

Sunflower

Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...

-shaped coronagraph

Coronagraph

A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved...

disc. A comparable proposal was also made for a satellite to occult bright X-ray sources, called an X-ray Occulting Steerable Satellite or XOSS.

Occultations and transits by planets between 1800 and 2100

This table lists occultations and transits of bright stars and planets by solar planets.

Day	Time (UT)	Foreground planet	Background object	Elongation
9 December 1802	07:36	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...	Acrab	16,2° West
9 December 1808	20:34	Mercury	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,...	20,3° West
22 December 1810	06:32	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...	Xi-2 Sagittarii Xi-2 Sagittarii Xi-2 Sagittarii is a spectral type G8 or K0 giant which has an apparent magnitude of +3.52. It is 372 light years from Earth....	11,1° East
3 January 1818	21:52	Venus	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,...	16,5° West
11 July 1825	09:10	Venus	Delta-1 Tauri	44,4° West
11 July 1837	12:50	Mercury	Eta Geminorum Eta Geminorum Eta Geminorum is a triple star system in the constellation Gemini. It has the traditional names Tejat Prior, Propus and Praepes and Pish Pai ....	17,8° West
9 May 1841	19:35	Venus	17 Tauri	9,2° East
27 September 1843	18:00	Venus	Eta Virginis Eta Virginis Eta Virginis is a star in the constellation Virgo. It has the traditional name Zaniah .Zaniah is about 204 light years distant from the Sun, and has apparent magnitude +3.9 and is of spectral type A2IV....	3,2° West
16 December 1850	11:28	Mercury	Lambda Sagittarii Lambda Sagittarii Lambda Sagittarii is a star within the constellation Sagittarius. The star marks the top of the Archer's bow, whence its traditional name Kaus Borealis. It also marks the top of the lid of the so-called "Teapot" asterism...	10,2° East
22 May 1855	05:04	Venus	Epsilon Geminorum Epsilon Geminorum Epsilon Geminorum is a star in the constellation of Gemini. It has the traditional name Mebsuta ....	37,4° East
30 June 1857	00:25	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,...	Delta Geminorum Delta Geminorum Delta Geminorum is a star in the constellation Gemini. It has the traditional name Wasat. The traditional name comes from the Arabic word for "middle"....	8,4° East
5 December 1865	14:20	Mercury	Lambda Sagittarii	21,0° East
28 February 1876	05:13	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,...	Acrab	97,6° West
7 June 1881	20:54	Mercury	Epsilon Geminorum	21,2° East
9 December 1906	17:40	Venus	Acrab	14,9° West
27 July 1910	02:53	Venus	Eta Geminorum	31,0° West
24 December 1937	18:38	Mercury	Omicron Sagittarii	11,6° East
10 June 1940	02:21	Mercury	Epsilon Geminorum	20,1° East
25 October 1947	01:45	Venus	Zuben-el-genubi (Alpha-2 Librae) Alpha Librae Alpha Librae is the second brightest star in the constellation Libra . It has the traditional name Zubenelgenubi. The name, from Arabic الزبن الجنوبي , means "southern claw" and was coined before Libra was recognized as distinct from Scorpius...	13,5° East
7 July 1959	14:30	Venus	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...	44,5° East
27 September 1965	15:30	Mercury	Eta Virginis Eta Virginis Eta Virginis is a star in the constellation Virgo. It has the traditional name Zaniah .Zaniah is about 204 light years distant from the Sun, and has apparent magnitude +3.9 and is of spectral type A2IV....	2.6° West
13 May 1971	20:00	Jupiter	Beta Scorpii (both components)	169,5° West
8 April 1976	01:00	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...	Epsilon Geminorum	81,3° East
17 November 1981	15:27	Venus	Nunki	47,0° East
19 November 1984	01:32	Venus	Lambda Sagittarii	39,2° East
4 December 2015	16.14	Mercury	Theta Ophiuchi	9,6° East
17 February 2035	15:19	Venus	Pi Sagittarii Pi Sagittarii Pi Sagittarii is a triple star system in the constellation Sagittarius. It has the traditional name Albaldah. It is known as 建三 in Chinese....	42,1° West
1 October 2044	22:00	Venus	Regulus	38,9° West
23 February 2046	19:24	Venus	Rho-1 Sagittarii	45,4° West
10 November 2052	07:20	Mercury	Zuben-el-genubi (Alpha-2 Librae) Alpha Librae Alpha Librae is the second brightest star in the constellation Libra . It has the traditional name Zubenelgenubi. The name, from Arabic الزبن الجنوبي , means "southern claw" and was coined before Libra was recognized as distinct from Scorpius...	2,8° West
22 November 2065	12:45	Venus	Jupiter	7,9° West
15 July 2067	11:56	Mercury	Neptune Neptune Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...	18,4° West
11 August 2069	20.25	Venus	Zavijava	38,4° East
3 October 2078	22:00	Mars	Theta Ophiuchi	71,4° East
11 August 2079	01:30	Mercury	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...	11,3° West
27 October 2088	13:43	Mercury	Jupiter	4,7° West
7 April 2094	10:48	Mercury	Jupiter	1,8° West

These events are not visible everywhere the occulting body and the occulted body are above the skyline. Some events are barely visible, because they take place in close proximity to the Sun.

Mutual planetary transits and occultations

In rare cases, one planet can transit in front of another. The next time this will happen (as seen from Earth) will be on November 22, 2065 at about 12:43 UTC

Coordinated Universal Time

Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...

, when Venus near superior conjunction (with an angular diameter

Angular diameter

The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...

of 10.6") will transit in front of 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,...

(with an angular diameter of 30.9"); however, this will take place only 8° west of the Sun, and will therefore not be visible to the unaided/unprotected eye. When the nearer object has a larger angular diameter

Angular diameter

than the farther object, thus covering it completely, the event is not a transit but an occultation. Before transiting Jupiter, Venus will occult Jupiter's moon

Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....

Ganymede

Ganymede (moon)

Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...

at around 11:24 UTC as seen from some southernmost parts of Earth. Parallax

Parallax

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

will cause actual observed times to vary by a few minutes, depending on the precise location of the observer.

There are only 18 mutual planetary transits and occultations as seen from Earth between 1700 and 2200. Note the long break of events between 1818 and 2065.

19 September 1702 – Jupiter occults Neptune
20 July 1705 – Mercury transits Jupiter
14 July 1708 – Mercury occults Uranus

4 October 1708 – Mercury transits Jupiter
28 May 1737 – Venus occults Mercury
29 August 1771 – Venus transits Saturn
21 July 1793 – Mercury occults Uranus
9 December 1808 – Mercury transits Saturn
3 January 1818 – Venus transits Jupiter
22 November 2065 – Venus transits Jupiter
15 July 2067 – Mercury occults Neptune
11 August 2079 – Mercury occults Mars
27 October 2088 – Mercury transits Jupiter
7 April 2094 – Mercury transits Jupiter
21 August 2104 – Venus occults Neptune
14 September 2123 – Venus transits Jupiter
29 July 2126 – Mercury occults Mars
3 December 2133 – Venus occults Mercury

The 1737 event was observed by John Bevis

John Bevis

John Bevis was an English doctor and astronomer. He is best known for discovering the Crab Nebula in 1731....

at Greenwich Observatory – it is the only detailed account of a mutual planetary occultation. A transit of Mars across Jupiter on 12 Sep 1170 was observed by the monk Gervase at Canterbury

Canterbury

Canterbury is a historic English cathedral city, which lies at the heart of the City of Canterbury, a district of Kent in South East England. It lies on the River Stour....

, and by Chinese astronomers. In addition, an occultation of Mars by Venus was observed by M. Möstlin

Michael Maestlin

Michael Maestlin was a German astronomer and mathematician, known for being the mentor of Johannes Kepler.-Career:...

at Heidelberg

Heidelberg

-Early history:Between 600,000 and 200,000 years ago, "Heidelberg Man" died at nearby Mauer. His jaw bone was discovered in 1907; with scientific dating, his remains were determined to be the earliest evidence of human life in Europe. In the 5th century BC, a Celtic fortress of refuge and place of...

on October 3, 1590.

Occultation in religion

In Shia Islam the Occultation
The Occultation
The Occultation in Shia Islam refers to a belief that the messianic figure, or Mahdi, who in Shi'i thought is an infallible male descendant of the founder of Islam, Muhammad, was born but disappeared, and will one day return and fill the world with justice. Some Shi'is, such as the Zaidi and...

is a term used to designate the hidden state of the Imam of the Time

Imamah (Shi'a doctrine)

Imāmah is the Shia doctrine of religious, spiritual and political leadership of the Ummah. The Shīa believe that the A'immah are the true Caliphs or rightful successors of Muḥammad, and further that Imams are possessed of divine knowledge and authority as well as being part of the Ahl al-Bayt,...

External links

Occultation Studies at Williams College
International Occultation Timing Association (IOTA)
Occultations of planets by other planets
Big Occulting Steerable Satellite
Moon, planets, asteroid occultations
Mutual occultations (and conjunctions) of planets
Society for Popular Astronomy – Occultation Section
SPACE.com: Discovery Hints at a Quadrillion Space Rocks Beyond Neptune (Sara Goudarzi) 15 August 2006 06:13 am ET
Scientists Use Novel Technique To Watch Occultations By Planets
Mutual Planetary Transits – Fifteen millennium catalog: 5 000 BC – 10 000 AD
asteroidoccultation.com/ Asteroid Occultation Updates
Occultations by asteroids (Good visual aid of an occultation of a star by Phoebe)
Society for Popular Astronomy (Asteroidal Occultations for the UK)
Occultations of HIP and UCAC2 stars downto 15m by large TNO in 2004–2014
Combining asteroid models derived by lightcurve inversion with asteroidal occultation silhouettes (arXiv : 21 Apr 2011)
Lunar Occultation Workbench, a free software package for computing lunar occultations

External references

Meeus, Jean: Astronomical Tables of the Sun, Moon and Planets. Richmond, Virginia: Willmann-Bell, Inc., 1995, ISBN 0-943396-45-X.

Marco Peuschel http://www.marco-peuschel.de, Astronomische Tabellen für den Mond von 2007 bis 2016,Mondphasen, Apsiden, Knotendurchgänge, Maximale und minimale Deklinationswerte und Sternbedeckungen sowie ausführliche Ephemeriden für jeden Tag des Jahres, inkl. Mondauf-und Untergänge und physische Daten.

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