Rosalind is an inner satellite of the planet Uranus.
Rosalind is the 12th largest Moon of Uranus and the 56th largest moon in the Solar System currently known.
Discovery
Rosalind was discovered by Stephen P. Synnott, who is an American astronomer and Voyager scientist, from the images taken by Voyager 2 on 13 January 1986.
Naming
The moon was given the temporary designation S/1986 U4.
The moon was named after the daughter of the banished Duke in William Shakespeare's play "As You Like It".
As You Like It is a pastoral comedy by William Shakespeare believed to have been written in 1599 or early 1600.
As You Like It follows its heroine Rosalind as she flees persecution in her uncle's court, accompanied by her cousin Celia and Touchstone the court jester, to find safety and eventually love in the Forest of Arden. Historically, critical response has varied, with some critics finding the work of lesser quality than other Shakespearean works and some finding the play a work of great merit.
Stats
Diameter (mean): 72 ± 12 km
Semi-major axis: 69,927 km
Orbital Period: 0.558 days
Orbit
Rosalind takes as long to rotate on its axis as it does to make one orbit of Uranus; and therefore always keeps the same hemisphere pointed to Uranus.
Rosalind belongs to a group of satellites called the Portia Group, which includes Bianca, Cressida, Desdemona, Portia, Juliet, Cupid, Belinda and Perdita. These satellites have similar orbits and photometric properties.
Rosalind is very close to a 3:5 orbital resonance with Cordelia.
Physical characteristics
Other than its orbit, diameter of 72 km and geometric albedo of 0.08, virtually nothing is known about Rosalind.
In the Voyager 2 images Rosalind appears as an almost spherical object. The ratio of axes of Rosalind's prolate spheroid is 0.8-1.0. Its surface is grey in color.
Exploration Status
No close-up image of Rosalind has been photographed.
No mission is planned in the foreseeable future.
Saturday 31 March 2012
Friday 30 March 2012
12th Largest Moon of Saturn - Prometheus (4th Moon outwards from Saturn)
Prometheus is an inner satellite of Saturn.
Prometheus is the 12th largest moon of Saturn, and the 49th largest moon in the Solar System currently known.
Discovery
Prometheus was discovered in 1980 (some time before October 25) from photos taken by the Voyager 1 probe.
Naming
Prometheus was provisionally designated S/1980 S27. In late 1985, the moon was officially named after Prometheus, a Titan in Greek mythology.
In Greek mythology, Prometheus is a Titan, the son of Iapetus and Clymene, and brother to Atlas, Epimetheus and Menoetius. He was a champion of mankind, known for his wily intelligence, who stole fire from Zeus and gave it to mortals. Zeus then punished him for his crime by having him bound to a rock while a great eagle ate his liver every day only to have it grow back to be eaten again the next day. His myth has been treated by a number of ancient sources, in which Prometheus is credited with – or blamed for – playing a pivotal role in the early history of mankind.
Stats
Diameter (mean): 86.2 ± 5.4 km
Semi-major axis: 139,380 km
Orbital Period: 0.613 days
Orbit
Prometheus rotates synchronously with its orbital period, keeping one face pointed toward Saturn.
Prometheus acts as a shepherd satellite for the inner edge of Saturn's F Ring. Recent images from the Cassini probe show that the Promethean gravitational field creates kinks and knots in the F Ring as the moon 'steals' material from it.
The orbit of Prometheus appears to be chaotic, as a consequence of a series of four 121:118 mean motion resonances with Pandora. The most appreciable changes in their orbits occur approximately every 6.2 years, when the periapsis of Pandora lines up with the apoapsis of Prometheus and the moons approach to within about 1400 km.
Prometheus is itself a significant perturber of Atlas, with which it is in a 53:54 mean longitude resonance.
Physical Characteristics
Prometheus is extremely elongated, measuring about 136 by 79 by 59 km. It has several ridges and valleys and a number of impact craters of about 20 km diameter are visible, but it is less cratered than nearby Pandora, Epimetheus and Janus.
From its very low density and relatively high albedo, it seems likely that Prometheus is a very porous icy body. There is a lot of uncertainty in these values, however, and so this remains to be confirmed.
Thursday 29 March 2012
12th Largest Moon of Jupiter - Sinope (62th Moon outwards from Jupiter)
Sinope is a retrograde irregular satellite of Jupiter and was the outermost known moon of Jupiter until the discovery of Megaclite in 2000. The most distant moon of Jupiter now known is S/2003 J2.
Sinope is the 12th largest moon of Jupiter and 74th largest moon in the Solar System currently known.
Discovery
Sinope was discovered by Seth Barnes Nicholson at Lick Observatory on July 21, 1914.
Naming
Sinope the moon is named after Sinope of Greek mythology.
In Greek Mythology, Sinope was one of the daughters of Asopus and thought to be an eponym of the city Sinope on the Black Sea.
According to Corinna and Diodorus Siculus, Sinope was seized by the god Apollo and carried over to the place where later stood the city honouring her name. Diodorus adds that she bore to Apollo a son named Syrus, supposedly afterwards king of the Syrians, who were named after him.
However, the Argonautica and Valerius Flaccus relate that Sinope was abducted to the site by Zeus, who, in his passion, swore to fulfil her dearest wish. Sinope declared she wished to remain a virgin. Sinope later tricked Apollo and the river Halys in the same fashion and remained a virgin all her life.
Stats
Diameter (mean): 38 km
Semi-major axis: 24,057,865 km
Orbital Period: -762.33 day
Orbit
Sinope orbits Jupiter on a high eccentricity and high inclination retrograde orbit. The orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.
It is often believed to belong to the Pasiphaë group. However, given its mean inclination and different colour, Sinope could be also an independent object, captured independently, unrelated to the collision and break-up at the origin of the group.
Sinope is also known to be in a secular resonance with Jupiter, similar to Pasiphae. However, Sinope can drop out of this resonance and has periods of both resonant and non resonant behaviour.
Physical characteristics
Sinope has an estimated diameter of 38 km (assuming an albedo of 0.04). The satellite is red, unlike Pasiphae which is grey.
Its infrared spectrum is similar to D-type asteroids and also different from Pasiphae. These dissimilarities of the physical parameters suggest a different origin from the core members of the group.
Sinope is the 12th largest moon of Jupiter and 74th largest moon in the Solar System currently known.
Discovery
Sinope was discovered by Seth Barnes Nicholson at Lick Observatory on July 21, 1914.
Naming
Sinope the moon is named after Sinope of Greek mythology.
In Greek Mythology, Sinope was one of the daughters of Asopus and thought to be an eponym of the city Sinope on the Black Sea.
According to Corinna and Diodorus Siculus, Sinope was seized by the god Apollo and carried over to the place where later stood the city honouring her name. Diodorus adds that she bore to Apollo a son named Syrus, supposedly afterwards king of the Syrians, who were named after him.
However, the Argonautica and Valerius Flaccus relate that Sinope was abducted to the site by Zeus, who, in his passion, swore to fulfil her dearest wish. Sinope declared she wished to remain a virgin. Sinope later tricked Apollo and the river Halys in the same fashion and remained a virgin all her life.
Stats
Diameter (mean): 38 km
Semi-major axis: 24,057,865 km
Orbital Period: -762.33 day
Orbit
Sinope orbits Jupiter on a high eccentricity and high inclination retrograde orbit. The orbital elements are as of January 2000. They are continuously changing due to solar and planetary perturbations.
It is often believed to belong to the Pasiphaë group. However, given its mean inclination and different colour, Sinope could be also an independent object, captured independently, unrelated to the collision and break-up at the origin of the group.
Sinope is also known to be in a secular resonance with Jupiter, similar to Pasiphae. However, Sinope can drop out of this resonance and has periods of both resonant and non resonant behaviour.
Physical characteristics
Sinope has an estimated diameter of 38 km (assuming an albedo of 0.04). The satellite is red, unlike Pasiphae which is grey.
Its infrared spectrum is similar to D-type asteroids and also different from Pasiphae. These dissimilarities of the physical parameters suggest a different origin from the core members of the group.
Monday 26 March 2012
Moon of 121 Hermione -- S/2002 (121) 1 "LaFayette"
The moon of 121 Hermione is the 6th largest moon of the asteroids currently known.
Discovery
The moon of 121 Hermione was discovered 28 September 2002 by W. J. Merline, P. M. Tamblyn, C. Dumas, L. M. Close, C. R. Chapman, F. Menard, W. M. Owen, D. C. Slater and J. Pepin using the Keck II telescope at Mauna Kea.
Naming
The moon was given the temporary designation S/2002 (121) 1, but has not yet received an official name.
"LaFayette" has been proposed by a group of astronomers in reference to the frigate used in secret by the Marquis de Lafayette to reach America to help the insurgents.
Stats
Diameter (estimated): 12 km (12 ± 4 km)
Semi-major axis: 768 ± 11 km
Orbital Period: 2.58 days
Rotation period: ?
Discovery
The moon of 121 Hermione was discovered 28 September 2002 by W. J. Merline, P. M. Tamblyn, C. Dumas, L. M. Close, C. R. Chapman, F. Menard, W. M. Owen, D. C. Slater and J. Pepin using the Keck II telescope at Mauna Kea.
Naming
The moon was given the temporary designation S/2002 (121) 1, but has not yet received an official name.
"LaFayette" has been proposed by a group of astronomers in reference to the frigate used in secret by the Marquis de Lafayette to reach America to help the insurgents.
Stats
Diameter (estimated): 12 km (12 ± 4 km)
Semi-major axis: 768 ± 11 km
Orbital Period: 2.58 days
Rotation period: ?
30th Largest Asteroid, 121 Hermione
121 Hermione is a large asteroid in the outer main asteroid belt. It is the 30th largest asteroid currently known.
Discovery
Hermione was discovered by James Craig Watson on May 12, 1872 from Ann Arbor, Michigan, USA.
Naming
Hermione the asteroid was named after Hermione, daughter of Menelaus and Helen in Greek mythology.
In Greek mythology, Menelaus was a legendary king of Mycenaean Sparta, the husband of Helen of Troy, and a central figure in the Trojan War.
Helen of Troy, also known as Helen of Sparta, was the daughter of Zeus and Leda (or Nemesis), step-daughter of King Tyndareus and wife of Menelaus. Her abduction by Paris brought about the Trojan War.
Stats
Diameter (mean): 190 km
Aphelion: 3.933 AU
Perihelion: 2.983 AU
Semi-major axis: 3.449 AU
Orbital Period: 6.41 years
Rotation period: 5.55 hrs
Date discovered: 1872.5.12
Class: C
Group: Cybele group
Type: Outer Main-belt Asteroid
Satellite: 1
(data from JPL Small-Body Database)
Orbit
Hermione is a Cybele asteroid and orbits beyond most of the main-belt asteroids.
Satellite
A satellite of Hermione was discovered in 2002 with the Keck II telescope.
Physical properties
Hermione is an asteroid of the dark C spectral type, and is probably composed of carbonaceous materials.
Hermione has a bi-lobed shape, as evidenced by adaptive optics images, the first of which were taken in December 2003, with the Keck telescope. Of several proposed shape models that agreed with the images, a "snowman"-like shape was found to best fit the observed precession rate of Hermione's satellite. In this "snowman" model, the asteroid's shape can be approximated by two partially overlapping spheres of radii 80 and 60 km, whose centers are separated by 115 km. A simple ellipsoid shape was ruled out.
Observation of the satellite's orbit has made possible an accurate determination of Hermione's mass. For the best-fit "snowman" model, the density is found to be 1.8 ± 0.2 g/cm³, giving a porosity of the order of 20%, and possibly indicating that the main components are fractured solid bodies, but that the asteroid is rather not a rubble pile.
Star Occultation
Occultations by Hermione have been successfully observed three times so far, the last time in February 16, 2004, when Hermione occulted TYC 1905-00864-1 in Gemini.
Discovery
Hermione was discovered by James Craig Watson on May 12, 1872 from Ann Arbor, Michigan, USA.
Naming
Hermione the asteroid was named after Hermione, daughter of Menelaus and Helen in Greek mythology.
In Greek mythology, Menelaus was a legendary king of Mycenaean Sparta, the husband of Helen of Troy, and a central figure in the Trojan War.
Helen of Troy, also known as Helen of Sparta, was the daughter of Zeus and Leda (or Nemesis), step-daughter of King Tyndareus and wife of Menelaus. Her abduction by Paris brought about the Trojan War.
Stats
Diameter (mean): 190 km
Aphelion: 3.933 AU
Perihelion: 2.983 AU
Semi-major axis: 3.449 AU
Orbital Period: 6.41 years
Rotation period: 5.55 hrs
Date discovered: 1872.5.12
Class: C
Group: Cybele group
Type: Outer Main-belt Asteroid
Satellite: 1
(data from JPL Small-Body Database)
Orbit
Hermione is a Cybele asteroid and orbits beyond most of the main-belt asteroids.
Satellite
A satellite of Hermione was discovered in 2002 with the Keck II telescope.
Physical properties
Hermione is an asteroid of the dark C spectral type, and is probably composed of carbonaceous materials.
Hermione has a bi-lobed shape, as evidenced by adaptive optics images, the first of which were taken in December 2003, with the Keck telescope. Of several proposed shape models that agreed with the images, a "snowman"-like shape was found to best fit the observed precession rate of Hermione's satellite. In this "snowman" model, the asteroid's shape can be approximated by two partially overlapping spheres of radii 80 and 60 km, whose centers are separated by 115 km. A simple ellipsoid shape was ruled out.
Observation of the satellite's orbit has made possible an accurate determination of Hermione's mass. For the best-fit "snowman" model, the density is found to be 1.8 ± 0.2 g/cm³, giving a porosity of the order of 20%, and possibly indicating that the main components are fractured solid bodies, but that the asteroid is rather not a rubble pile.
Star Occultation
Occultations by Hermione have been successfully observed three times so far, the last time in February 16, 2004, when Hermione occulted TYC 1905-00864-1 in Gemini.
Moon of asteroid 702 Alauda -- Pichi üñëm
The moon of 702 Alauda is the 12th largest moon of the asteroids currently known.
Discovery
P . Rojo, Universidad de Chile; and J. L. Margot, Cornell University, reported the discovery on July 26, 2007 of a satellite of 702 Alauda from adaptive-optics imaging with the ESO 8-m Very Large Telescope UT4/YEPUN on Cerro Paranal, Chile.
The satellite was observed at two epochs on each of two consecutive nights. On July 26, the companion was at a separation of 0".58 (projected separation about 900 km).
The primary-to-secondary H-band flux ratio is about 1250, yielding a diameter ratio of about 35.
Naming
The moon was given the temporary designation S/2007(702)1.
The moon has been named Pichi üñëm, which means "little bird" in the Mapuche language of Chile, the country from which the moon was discovered.
Stats
Diameter (estimated): 5.5 km
Semi-major axis: 900 km
Orbital Period: 3 days ?
Rotation period: ?
Discovery
P . Rojo, Universidad de Chile; and J. L. Margot, Cornell University, reported the discovery on July 26, 2007 of a satellite of 702 Alauda from adaptive-optics imaging with the ESO 8-m Very Large Telescope UT4/YEPUN on Cerro Paranal, Chile.
The satellite was observed at two epochs on each of two consecutive nights. On July 26, the companion was at a separation of 0".58 (projected separation about 900 km).
The primary-to-secondary H-band flux ratio is about 1250, yielding a diameter ratio of about 35.
Naming
The moon was given the temporary designation S/2007(702)1.
The moon has been named Pichi üñëm, which means "little bird" in the Mapuche language of Chile, the country from which the moon was discovered.
Stats
Diameter (estimated): 5.5 km
Semi-major axis: 900 km
Orbital Period: 3 days ?
Rotation period: ?
Sunday 25 March 2012
29th Largest Asteroid, 702 Alauda
702 Alauda is a large asteroid and the 29th largest asteroid currently known.
Discovery
702 Alauda was discovered on 16 July 1910 by Joseph Helffrich at Heidelberg.
Naming
Alauda the asteroid was named after the Alaudidae family of birds (the larks).
Larks are passerine birds of the family Alaudidae. All species occur in the Old World, and in northern and eastern Australia; only one, the Shore Lark, has spread to North America, where it is called the Horned Lark.
Stats
Diameter (mean): 195 km
Aphelion: 3.261 AU
Perihelion: 3.129 AU
Semi-major axis: 3.195 AU
Orbital Period: 5.71 years
Rotation period: 8.35 hrs
Date discovered: 1910.7.16
Class: C
Satellite: 1
Group: Alauda Group
Type: Main-belt Asteroid
(data from JPL Small-Body Database)
Satellite
Alauda's satellite, Pichi üñëm, was discovered in 2007 from observations using adaptive-optics imaging with the European Southern Observatory (ESO) 8-m Very Large Telescope (VLT) on Cerro Paranal, Chile.
Orbital characteristics
Alauda has been identified as the largest member of a dynamical family. Alauda's moon may be a result of the collision that created the asteroid family.
Physical characteristics
The discovery of Alauda's moon enabled Alauda's mass to be determined. Rojo and Margot (2010) have estimated its mass to be 6.06×1018 kg with a density of 1.57 g/cm³.
Star Occultations
Alauda has been observed to occult stars on several occasions, providing important information on its size and shape. Alauda produced occultations on 2001-07-12 (on SAO 188447) and 2009-10-17 (on TYC 1920-00620-1).
Discovery
702 Alauda was discovered on 16 July 1910 by Joseph Helffrich at Heidelberg.
Naming
Alauda the asteroid was named after the Alaudidae family of birds (the larks).
Larks are passerine birds of the family Alaudidae. All species occur in the Old World, and in northern and eastern Australia; only one, the Shore Lark, has spread to North America, where it is called the Horned Lark.
Stats
Diameter (mean): 195 km
Aphelion: 3.261 AU
Perihelion: 3.129 AU
Semi-major axis: 3.195 AU
Orbital Period: 5.71 years
Rotation period: 8.35 hrs
Date discovered: 1910.7.16
Class: C
Satellite: 1
Group: Alauda Group
Type: Main-belt Asteroid
(data from JPL Small-Body Database)
Satellite
Alauda's satellite, Pichi üñëm, was discovered in 2007 from observations using adaptive-optics imaging with the European Southern Observatory (ESO) 8-m Very Large Telescope (VLT) on Cerro Paranal, Chile.
Orbital characteristics
Alauda has been identified as the largest member of a dynamical family. Alauda's moon may be a result of the collision that created the asteroid family.
Physical characteristics
The discovery of Alauda's moon enabled Alauda's mass to be determined. Rojo and Margot (2010) have estimated its mass to be 6.06×1018 kg with a density of 1.57 g/cm³.
Star Occultations
Alauda has been observed to occult stars on several occasions, providing important information on its size and shape. Alauda produced occultations on 2001-07-12 (on SAO 188447) and 2009-10-17 (on TYC 1920-00620-1).
28th Largest Asteroid, 24 Themis
24 Themis is a large main-belt asteroids and the largest member of the Themistian asteroid family. Themis is the 28th largest asteroid currently known.
Discovery
24 Themis was discovered on 5 April 1853 by Annibale de Gasparis at Naples.
Naming
Themis the asteroid was named after Themis, the Greek goddess of law.
Themis is an ancient Greek Titaness. She is described as "of good counsel", and is the embodiment of divine order, law and custom.
Themis was named by Angelo Secchi, who was Director of the Observatory at the Pontifical Gregorian University (then called the Roman College). He was a pioneer in astronomical spectroscopy, and was one of the first scientists to state authoritatively that the Sun is a star.
Stats
Diameter (mean): 198 km
Aphelion: 3.539 AU
Perihelion: 2.732 AU
Semi-major axis: 3.316 AU
Orbital Period: 5.55 years
Rotation period: 8.37 hrs
Date discovered: 1853.4.5
Class: C
Group: Themis Group
Type: Main-belt Asteroid
(data from JPL Small-Body Database)
Orbit and rotation
Themis is in an elliptical orbit around the Sun with an eccentricity of 0.1306 and an inclination of 0.76°.
Themis is part of the Themis family of asteroids, which is located in the outer part of the main belt. The family consists of a core of large objects surrounded by a cloud of smaller objects; 24 Themis is a member of the core.
Surface ice
On October 7, 2009, the presence of water ice was confirmed on the surface of Themis using NASA’s Infrared Telescope Facility. The surface of Themis appears completely covered in ice. As this ice layer is sublimated, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface.
Scientists hypothesize that some of the first water brought to Earth was delivered by asteroid impacts after the collision that produced the Moon. The presence of ice on 24 Themis supports this theory. Because of its proximity to the sun (~3.3 AU), the widespread ice on the surface of 24 Themis is somewhat unexpected. The surface ice may be replenished by a sub-surface reservoir of water.
An alternative mechanism to explain the presence of water ice on Themis is similar to the hypothesized formation of water on the surface of the Moon by solar wind. Trace amounts of water would be continuously produced by high-energy solar protons impinging oxide minerals present at the surface of Themis.
Discovery
24 Themis was discovered on 5 April 1853 by Annibale de Gasparis at Naples.
Naming
Themis the asteroid was named after Themis, the Greek goddess of law.
Themis is an ancient Greek Titaness. She is described as "of good counsel", and is the embodiment of divine order, law and custom.
Themis was named by Angelo Secchi, who was Director of the Observatory at the Pontifical Gregorian University (then called the Roman College). He was a pioneer in astronomical spectroscopy, and was one of the first scientists to state authoritatively that the Sun is a star.
Stats
Diameter (mean): 198 km
Aphelion: 3.539 AU
Perihelion: 2.732 AU
Semi-major axis: 3.316 AU
Orbital Period: 5.55 years
Rotation period: 8.37 hrs
Date discovered: 1853.4.5
Class: C
Group: Themis Group
Type: Main-belt Asteroid
(data from JPL Small-Body Database)
Orbit and rotation
Themis is in an elliptical orbit around the Sun with an eccentricity of 0.1306 and an inclination of 0.76°.
Themis is part of the Themis family of asteroids, which is located in the outer part of the main belt. The family consists of a core of large objects surrounded by a cloud of smaller objects; 24 Themis is a member of the core.
Surface ice
On October 7, 2009, the presence of water ice was confirmed on the surface of Themis using NASA’s Infrared Telescope Facility. The surface of Themis appears completely covered in ice. As this ice layer is sublimated, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface.
Scientists hypothesize that some of the first water brought to Earth was delivered by asteroid impacts after the collision that produced the Moon. The presence of ice on 24 Themis supports this theory. Because of its proximity to the sun (~3.3 AU), the widespread ice on the surface of 24 Themis is somewhat unexpected. The surface ice may be replenished by a sub-surface reservoir of water.
An alternative mechanism to explain the presence of water ice on Themis is similar to the hypothesized formation of water on the surface of the Moon by solar wind. Trace amounts of water would be continuously produced by high-energy solar protons impinging oxide minerals present at the surface of Themis.
Tuesday 20 March 2012
27th Largest Asteroid, 7 Iris
Among the S-type asteroids, it ranks fifth in geometric mean diameter after Eunomia, Juno, Herculina and Amphitrite.
Discovery
Iris was the seventh asteroid discovered, on August 13, 1847, by John Russell Hind from London. Iris was Hind's first asteroid discovery.
Naming
Iris was named after the rainbow goddess Iris of Greek mythology, sister of the Harpies and messenger of the gods, especially Hera. Her quality of attendant of Hera was particularly appropriate to the circumstances of discovery, as Iris was spotted following 3 Juno (Juno is the Roman equivalent of Hera) by less than an hour of right ascension.
In Greek mythology, Iris is the personification of the rainbow and messenger of the gods. She is also known as one of the goddesses of the sea and the sky. Iris links the gods to humanity. She travels with the speed of wind from one end of the world to the other, and into the depths of the sea and the underworld.
Stats
Diameter (mean): 200 km
Aphelion: 2.937 AU
Perihelion: 1.824 AU
Semi-major axis: 2.387 AU
Orbital Period: 3.69 years
Rotation period: 7.139 hrs
Date discovered: 1847.8.13
Class: S
Type: Main-belt Asteroid
(data from JPL Small-Body Database)
Brightness
Iris's bright surface and small distance from the Sun make it the fourth brightest object in the asteroid belt after Vesta, Ceres, and Pallas. But at typical oppositions it marginally outshines the larger though darker Pallas.
Iris has a mean opposition magnitude of +7.8, comparable to that of Neptune, and can easily be seen with binoculars at most oppositions. At rare oppositions near perihelion Iris can reach a magnitude of +6.7 (next time on October 31st, 2017 reaching a magnitude of +6.9), which is as bright as Ceres ever gets. Reports of Iris being seen without optical aid are unverified.
Characteristics
Lightcurve analysis indicates a somewhat angular shape and that Iris' pole points towards ecliptic coordinates with a 10° uncertainty. This gives an axial tilt of 85°, so that on almost a whole hemisphere of Iris, the sun does not set during summer, and does not rise during winter. On an airless body this gives rise to very large temperature differences.
The Iridian surface likely exhibits albedo differences, with possibly a large bright area in the northern hemisphere. Overall the surface is very bright and is probably a mixture nickel-iron metals and magnesium- and iron-silicates. Its spectrum is similar to that of L and LL chondrites with corrections for space weathering, so it may be an important contributor of these meteorites. Planetary dynamics also indicates that it should be a significant source of meteorites.
Star Occultation
Iris was observed occulting a star on May 26, 1995, and later on July 25, 1997. Both observations gave a diameter of about 200 km.
Monday 19 March 2012
Moon of asteroid 624 Hektor -- S/2006 (624) 1
The moon of 624 Hektor is the 4th largest moon of the asteroids currently known.
Discovery
On 16 July 2006, a satellite of Hektor was found by F. Marchis, M. H. Wong, J. Berthier, P. Descamps, D. Hestroffer, F. Vachier, D. Le Mignant and I. de Pater based on observations from the Keck-II adaptive optics telescope.
Naming
The moon was given the temporary designation S/2006(624)1, but has not yet received an official name.
Stats
Diameter (estimated): 15 km
Semi-major axis: 1000 km
Orbital Period: 2.08 days
Rotation period: ?
Discovery
On 16 July 2006, a satellite of Hektor was found by F. Marchis, M. H. Wong, J. Berthier, P. Descamps, D. Hestroffer, F. Vachier, D. Le Mignant and I. de Pater based on observations from the Keck-II adaptive optics telescope.
Naming
The moon was given the temporary designation S/2006(624)1, but has not yet received an official name.
Stats
Diameter (estimated): 15 km
Semi-major axis: 1000 km
Orbital Period: 2.08 days
Rotation period: ?
Sunday 18 March 2012
26th Largest Asteroid, 624 Hektor [Largest Jupiter Trojan]
624 Hektor is the largest Jupiter Trojan and is the 26th largest asteroid currently known.
Discovery
624 Hektor was discovered on Feb 10, 1907 by August Kopff at Heidelberg.
Naming
Hektor is named after the Trojan hero Hektor.
In Greek mythology, Hectōr or Hektōr, was a Trojan prince and the greatest fighter for Troy in the Trojan War. He acts as leader of the Trojans and their allies in the defense of Troy, killing 31 Greek fighters in all.
Stats
Diameter (mean): 203 km
Aphelion: 5.349 AU
Perihelion: 5.121 AU
Semi-major axis: 5.243 AU
Orbital Period: 12.01 years
Rotation period: 6.924 hrs
Date discovered: 1907.2.10
Class: D
Satellite: 1
Type: Jupiter Trojan
(data from JPL Small-Body Database)
Orbit
Hektor is a D-type asteroid, dark and reddish in colour. It lies in Jupiter's leading Lagrangian point, L4, called the 'Greek' node after one of the two sides in the legendary Trojan War.
Hektor is thus one of two trojan asteroids that is "misplaced" in the wrong camp (the other being 617 Patroclus in the Trojan node).
Formation
Hektor is found to be a truly extraordinary object in that it is larger and far more irregular in shape than other measured Trojans and far more irregular than other belt asteroids of comparable size.
It is proposed that Hektor could be a partially coalesced pair of Trojan asteroids which collided with energy too low to cause complete fragmentation, thus forming a dumbbell-shaped object.
Contact binary plus moonlet
Hektor is one of the most elongated bodies of its size in the Solar System, being 370 × 200 km. It is thought that Hektor might be a contact binary. Hubble Space Telescope observations of Hektor in 1993 did not show an obvious bilobate shape because of a limited angular resolution.
On 17 July 2006, the Keck-10m II telescope and its Laser guide star Adaptive Optics (AO) system indicated a bilobate shape for Hektor.
Additionally, a 15-km moonlet at 1000 km of Hektor was detected. The satellite's provisional designation is S/2006(624)1.
Hektor is, so far, the only known binary trojan asteroid in the L4 point and the first trojan with a satellite companion.
Discovery
624 Hektor was discovered on Feb 10, 1907 by August Kopff at Heidelberg.
Naming
Hektor is named after the Trojan hero Hektor.
In Greek mythology, Hectōr or Hektōr, was a Trojan prince and the greatest fighter for Troy in the Trojan War. He acts as leader of the Trojans and their allies in the defense of Troy, killing 31 Greek fighters in all.
Stats
Diameter (mean): 203 km
Aphelion: 5.349 AU
Perihelion: 5.121 AU
Semi-major axis: 5.243 AU
Orbital Period: 12.01 years
Rotation period: 6.924 hrs
Date discovered: 1907.2.10
Class: D
Satellite: 1
Type: Jupiter Trojan
(data from JPL Small-Body Database)
Orbit
Hektor is a D-type asteroid, dark and reddish in colour. It lies in Jupiter's leading Lagrangian point, L4, called the 'Greek' node after one of the two sides in the legendary Trojan War.
Hektor is thus one of two trojan asteroids that is "misplaced" in the wrong camp (the other being 617 Patroclus in the Trojan node).
Formation
Hektor is found to be a truly extraordinary object in that it is larger and far more irregular in shape than other measured Trojans and far more irregular than other belt asteroids of comparable size.
It is proposed that Hektor could be a partially coalesced pair of Trojan asteroids which collided with energy too low to cause complete fragmentation, thus forming a dumbbell-shaped object.
Contact binary plus moonlet
Hektor is one of the most elongated bodies of its size in the Solar System, being 370 × 200 km. It is thought that Hektor might be a contact binary. Hubble Space Telescope observations of Hektor in 1993 did not show an obvious bilobate shape because of a limited angular resolution.
On 17 July 2006, the Keck-10m II telescope and its Laser guide star Adaptive Optics (AO) system indicated a bilobate shape for Hektor.
Additionally, a 15-km moonlet at 1000 km of Hektor was detected. The satellite's provisional designation is S/2006(624)1.
Hektor is, so far, the only known binary trojan asteroid in the L4 point and the first trojan with a satellite companion.
Moons of outer solar system - Vanth (moon of Orcus)
Vanth, officially (90482) Orcus I Vanth, is the single known natural satellite of the plutino and likely dwarf planet Orcus.
Vanth is the 23th largest moon in the Solar System currently known.
Discovery
Vanth was discovered by Mike Brown and T.-A. Suer using discovery images taken by the Hubble Space Telescope on November 13, 2005. The discovery was announced on 22 February, 2007 in IAUC 8812.
Naming
Upon discovery, Vanth was issued a provisional designation, S/2005 (90482) 1. On March 23, 2009, Brown asked readers of his weekly column to suggest possible names for the satellite, with the best one to be submitted to the International Astronomical Union (IAU) on April 5.
The name Vanth, the winged Etruscan psychopomp who guides the souls of the dead to the underworld, was chosen from among a large pool of submissions.
Vanth was the only suggestion that was purely Etruscan in origin. It was the most popular submission, first suggested by Sonya Taaffe.
The Etruscan Vanth is frequently portrayed in the company of Charun (Charon), and so as the name of the moon of Orcus (nicknamed the "anti-Pluto" because resonance with Neptune keeps it on the opposite side of the Sun from Pluto), it is an allusion to the parallels between Orcus and Pluto.
Stats
Diameter (estimated): 280 km (280 - 380 km)
Semi-major axis: 9030 ± 89 km
Orbital Period: 9.54 days
Rotation Period: Synchronous
Orbit
Vanth orbits Orcus "in a tight precise circle", with a period of approximately 10 days.
Michael E. Brown suspects that, like Pluto and Charon, Orcus and Vanth are tidally locked.
Formation
The satellite does not resemble other known collisional satellites because its spectrum is very different of that of primary and thus may be a captured KBO.
Physical Properties
Vanth was found at 0.25 arcsec from Orcus with magnitude difference of 2.7 ± 1.0. Estimates made in 2009 by Mike Brown show that the apparent magnitude of Vanth is 21.97 ± 0.05 which is 2.54 ± 0.01 magnitudes fainter than Orcus. Assuming equal albedos this would mean a diameter of 280 km, or 2.9 times smaller than the primary.
However, the dissimilar colors of Orcus (neutral) and Vanth (red) suggest that Vanth could have an albedo a factor of two lower than Orcus. Should Vanth have an albedo of only 0.12, Vanth could be as large as 380 km with Orcus being 760 km in diameter. The mass of Vanth also depends on its albedo and can vary from 3 to 9% of the total system mass.
Vanth is the 23th largest moon in the Solar System currently known.
Discovery
Vanth was discovered by Mike Brown and T.-A. Suer using discovery images taken by the Hubble Space Telescope on November 13, 2005. The discovery was announced on 22 February, 2007 in IAUC 8812.
Naming
Upon discovery, Vanth was issued a provisional designation, S/2005 (90482) 1. On March 23, 2009, Brown asked readers of his weekly column to suggest possible names for the satellite, with the best one to be submitted to the International Astronomical Union (IAU) on April 5.
The name Vanth, the winged Etruscan psychopomp who guides the souls of the dead to the underworld, was chosen from among a large pool of submissions.
Vanth was the only suggestion that was purely Etruscan in origin. It was the most popular submission, first suggested by Sonya Taaffe.
The Etruscan Vanth is frequently portrayed in the company of Charun (Charon), and so as the name of the moon of Orcus (nicknamed the "anti-Pluto" because resonance with Neptune keeps it on the opposite side of the Sun from Pluto), it is an allusion to the parallels between Orcus and Pluto.
Stats
Diameter (estimated): 280 km (280 - 380 km)
Semi-major axis: 9030 ± 89 km
Orbital Period: 9.54 days
Rotation Period: Synchronous
Orbit
Vanth orbits Orcus "in a tight precise circle", with a period of approximately 10 days.
Michael E. Brown suspects that, like Pluto and Charon, Orcus and Vanth are tidally locked.
Formation
The satellite does not resemble other known collisional satellites because its spectrum is very different of that of primary and thus may be a captured KBO.
Physical Properties
Vanth was found at 0.25 arcsec from Orcus with magnitude difference of 2.7 ± 1.0. Estimates made in 2009 by Mike Brown show that the apparent magnitude of Vanth is 21.97 ± 0.05 which is 2.54 ± 0.01 magnitudes fainter than Orcus. Assuming equal albedos this would mean a diameter of 280 km, or 2.9 times smaller than the primary.
However, the dissimilar colors of Orcus (neutral) and Vanth (red) suggest that Vanth could have an albedo a factor of two lower than Orcus. Should Vanth have an albedo of only 0.12, Vanth could be as large as 380 km with Orcus being 760 km in diameter. The mass of Vanth also depends on its albedo and can vary from 3 to 9% of the total system mass.
(55637) 2002 UX25 - 18th Largest TNO? 7th Largest Cubewano ?
2002 UX25 is a large trans-Neptunian object. 2002 UX25 is possibly the 18th largest TNO and 7th largest Cubewano currently known.
Discovery
2002 UX25 was discovered on October 30, 2002, by the Spacewatch program at Kitt Peak.
2002 UX25 has precovery images back to 1991.
Stats
Estimated Diameter: 681 km (567 - 797 km)
Aphelion: 48.92 AU
Perihelion: 36.77 AU
Semi-major axis: 42.94 AU
Orbital Period: 281.41 years
Rotation period: 14.38 hours
Date discovered: 2002.10.30
Satellite: 1
Classification: TNO, KBO - Cubewano
Orbit
2002 UX25 is a Spitzer dwarf-planet candidate that orbits the Sun in the Kuiper belt beyond Neptune. It takes roughly 281 years to orbit the Sun.
2002 UX25 has a perihelion (closest approach to the Sun) of 36.77 AU, which it will next reach in 2065. As of 2010, 2002 UX25 is 41 AU from the Sun.
Physical Characteristics
A variability of the visual brightness was detected which could be fit to a period of 14.38 or 16.78 h rotation period (depending on a single-peaked or double peaked curve).
The Spitzer Space Telescope has estimated it to have a size of 681 +116 or
−114 km.
Satellite
The discovery of a satellite of 2002 UX25 was reported in IAUC 8812 on 22 February 2007.
The satellite was detected using the Hubble Space Telescope in August 2005. The orbit of this satellite has yet to be determined. The satellite was found at 0.16 arcsec from the primary with an apparent magnitude difference of 2.5. Assuming a similar albedo the magnitude suggests the satellite has a diameter of 205 ± 55 km.
How big is it?
2002 UX25 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf planet candidate?
2002 UX25 has an absolute magnitude of 3.6, making it a dwarf planet candidate. The Spitzer Space Telescope has estimated 2002 UX25 to have a diameter of about 681 km, and most icy objects around 400 km in diameter are believed to be spherical.
Michael E. Brown's automatically updated website lists it as a highly likely dwarf planet, and Michael E. Brown called it a probable dwarf planet. But light curve analysis has questioned whether it would truly qualify as a dwarf planet.
Discovery
2002 UX25 was discovered on October 30, 2002, by the Spacewatch program at Kitt Peak.
2002 UX25 has precovery images back to 1991.
Stats
Estimated Diameter: 681 km (567 - 797 km)
Aphelion: 48.92 AU
Perihelion: 36.77 AU
Semi-major axis: 42.94 AU
Orbital Period: 281.41 years
Rotation period: 14.38 hours
Date discovered: 2002.10.30
Satellite: 1
Classification: TNO, KBO - Cubewano
Orbit
2002 UX25 is a Spitzer dwarf-planet candidate that orbits the Sun in the Kuiper belt beyond Neptune. It takes roughly 281 years to orbit the Sun.
2002 UX25 has a perihelion (closest approach to the Sun) of 36.77 AU, which it will next reach in 2065. As of 2010, 2002 UX25 is 41 AU from the Sun.
Physical Characteristics
A variability of the visual brightness was detected which could be fit to a period of 14.38 or 16.78 h rotation period (depending on a single-peaked or double peaked curve).
The Spitzer Space Telescope has estimated it to have a size of 681 +116 or
−114 km.
Satellite
The discovery of a satellite of 2002 UX25 was reported in IAUC 8812 on 22 February 2007.
The satellite was detected using the Hubble Space Telescope in August 2005. The orbit of this satellite has yet to be determined. The satellite was found at 0.16 arcsec from the primary with an apparent magnitude difference of 2.5. Assuming a similar albedo the magnitude suggests the satellite has a diameter of 205 ± 55 km.
How big is it?
2002 UX25 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf planet candidate?
2002 UX25 has an absolute magnitude of 3.6, making it a dwarf planet candidate. The Spitzer Space Telescope has estimated 2002 UX25 to have a diameter of about 681 km, and most icy objects around 400 km in diameter are believed to be spherical.
Michael E. Brown's automatically updated website lists it as a highly likely dwarf planet, and Michael E. Brown called it a probable dwarf planet. But light curve analysis has questioned whether it would truly qualify as a dwarf planet.
Saturday 17 March 2012
(208996) 2003 AZ84 - 17th Largest TNO? 3rd Largest Plutino ?
(208996) 2003 AZ84, is a plutino, like Pluto, in a 2:3 resonance with Neptune. 2003 AZ84 is possibly the 17th largest TNO and 3rd largest Plutino currently known.
Discovery
2003 AZ84 was discovered on January 13, 2003 by Michael E. Brown and Chadwick A. Trujillo using the Samuel Oschin telescope in the Palomar Observatory.
Stats
Estimated Diameter: 685 km (686 ± 96 km)
Aphelion: 46.48 AU
Perihelion: 32.61 AU
Semi-major axis: 39.56 AU
Orbital Period: 248.81 years
Rotation period: 13.42 hours
Date discovered: 2003.1.13
Satellite: 1 ?
Classification: TNO, KBO - Plutino
Orbit
2003 AZ84 is classified as a plutino, which means that it is in a 3:2 orbital resonance with Neptune, similar to that of Pluto. It orbits the Sun in just over 248 Earth years.
2003 AZ84 is currently 45.3 AU from the Sun and came to aphelion (farthest distance from the Sun) in 1982. It will come to perihelion in 2107.
Physical characteristics
The Spitzer Space Telescope has estimated 2003 AZ84 to have a size of 686 ± 96 km, while an analysis of a combination of Spitzer and Hershel data yielded a somewhat higher estimate of 910 ± 60 km.
The spectra and colors of 2003 AZ84 are very similar to those of Orcus, another large planetoid in 3:2 resonance with Neptune. Both bodies have a flat featureless spectrum in the visible and moderately strong water ice absorption bands in the near-infrared, although 2003 AZ84 has a lower albedo. Both bodies also have a weak absorption band near 2.3 μm, which may be caused by ammonia hydrate or methane ice.
A stellar occultation in 2010 measured a single chord of 573 ± 21 km. But this is only a lower limit for the diameter of 2003 AZ84 as the chord may not have passed through the center of the body.
Satellite
Using observations with the Hubble Space Telescope, the discovery of a satellite of 2003 AZ84 was reported in IAUC 8812 on 22 February 2007.
The object was measured with a separation of 0.22 arcsec and an apparent magnitude difference of 5.0.
As of 2012, attempts to recover the satellite have failed. The unrecovered satellite is estimated to be about 68 ± 20 km in diameter.
How big is it?
2003 AZ84 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Discovery
2003 AZ84 was discovered on January 13, 2003 by Michael E. Brown and Chadwick A. Trujillo using the Samuel Oschin telescope in the Palomar Observatory.
Stats
Estimated Diameter: 685 km (686 ± 96 km)
Aphelion: 46.48 AU
Perihelion: 32.61 AU
Semi-major axis: 39.56 AU
Orbital Period: 248.81 years
Rotation period: 13.42 hours
Date discovered: 2003.1.13
Satellite: 1 ?
Classification: TNO, KBO - Plutino
Orbit
2003 AZ84 is classified as a plutino, which means that it is in a 3:2 orbital resonance with Neptune, similar to that of Pluto. It orbits the Sun in just over 248 Earth years.
2003 AZ84 is currently 45.3 AU from the Sun and came to aphelion (farthest distance from the Sun) in 1982. It will come to perihelion in 2107.
Physical characteristics
The Spitzer Space Telescope has estimated 2003 AZ84 to have a size of 686 ± 96 km, while an analysis of a combination of Spitzer and Hershel data yielded a somewhat higher estimate of 910 ± 60 km.
The spectra and colors of 2003 AZ84 are very similar to those of Orcus, another large planetoid in 3:2 resonance with Neptune. Both bodies have a flat featureless spectrum in the visible and moderately strong water ice absorption bands in the near-infrared, although 2003 AZ84 has a lower albedo. Both bodies also have a weak absorption band near 2.3 μm, which may be caused by ammonia hydrate or methane ice.
A stellar occultation in 2010 measured a single chord of 573 ± 21 km. But this is only a lower limit for the diameter of 2003 AZ84 as the chord may not have passed through the center of the body.
Satellite
Using observations with the Hubble Space Telescope, the discovery of a satellite of 2003 AZ84 was reported in IAUC 8812 on 22 February 2007.
The object was measured with a separation of 0.22 arcsec and an apparent magnitude difference of 5.0.
As of 2012, attempts to recover the satellite have failed. The unrecovered satellite is estimated to be about 68 ± 20 km in diameter.
How big is it?
2003 AZ84 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Wednesday 14 March 2012
(278361) 2007 JJ43 - 16th Largest TNO?
(278361) 2007 JJ43 is a large trans-Neptunian object (TNO). 2007 JJ43 is possibly the 16th largest TNO currently known.
Discovery
2007 JJ43's discovery images were taken on May 14, 2007 at Palomar Observatory.
Stats
Estimated Diameter: 694 km (650 - 800 km)
Aphelion: 55.37 AU
Perihelion: 40.29 AU
Semi-major axis: 47.8 AU
Orbital Period: 330.53 years
Rotation period: ? hours
Date discovered: 2007.5.14
Satellite: ?
Classification: TNO, other
Orbit
2007 JJ43 is orbiting the Sun near the outer edge of the Kuiper belt. As of 2012, 2007 JJ43 is about 41.5 AU from the Sun.
How big is it?
2007 JJ43 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
2007 JJ43's absolute magnitude of 3.7 is one of the twenty brightest exhibited by TNOs. Assuming it has a typical albedo, this would make it roughly the same size as Ixion (~650–800 km diameter).
Mike Brown's automatically updated website lists it as a highly likely dwarf planet, but the diameter of the object has never been measured.
Discovery
2007 JJ43's discovery images were taken on May 14, 2007 at Palomar Observatory.
Stats
Estimated Diameter: 694 km (650 - 800 km)
Aphelion: 55.37 AU
Perihelion: 40.29 AU
Semi-major axis: 47.8 AU
Orbital Period: 330.53 years
Rotation period: ? hours
Date discovered: 2007.5.14
Satellite: ?
Classification: TNO, other
Orbit
2007 JJ43 is orbiting the Sun near the outer edge of the Kuiper belt. As of 2012, 2007 JJ43 is about 41.5 AU from the Sun.
How big is it?
2007 JJ43 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
2007 JJ43's absolute magnitude of 3.7 is one of the twenty brightest exhibited by TNOs. Assuming it has a typical albedo, this would make it roughly the same size as Ixion (~650–800 km diameter).
Mike Brown's automatically updated website lists it as a highly likely dwarf planet, but the diameter of the object has never been measured.
Saturday 10 March 2012
(307261) 2002 MS4 - 15th Largest TNO? 6th Largest Cubewano ?
2002 MS4 is a large trans-Neptunian object. 2002 MS4 is possibly the 15th largest TNO and 6th largest Cubewano currently known.
Discovery
2002 MS4 is discovered on June 18, 2002 by Michael E. Brown and Chadwick A. Trujillo at Palomar Observatory.
2002 MS4 has precovery images back to 1954.
Stats
Estimated Diameter: 726 km (603 - 849 km)
Aphelion: 47.86 AU
Perihelion: 35.51 AU
Semi-major axis: 41.67 AU
Orbital Period: 268.98 years
Rotation period: 16.34 hours
Date discovered: 2002.6.18
Satellite: ?
Classification: TNO, KBO - Cubewano
Orbit
2002 MS4 currently 47.2 AU from the Sun and will come to perihelion around 2122.
How big is it?
2002 MS4 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
Mike Brown's automatically updated website lists it as a highly likely dwarf planet.
The Spitzer Space Telescope has estimated it to have a diameter of 726 ± 123 km.
Discovery
2002 MS4 is discovered on June 18, 2002 by Michael E. Brown and Chadwick A. Trujillo at Palomar Observatory.
2002 MS4 has precovery images back to 1954.
Stats
Estimated Diameter: 726 km (603 - 849 km)
Aphelion: 47.86 AU
Perihelion: 35.51 AU
Semi-major axis: 41.67 AU
Orbital Period: 268.98 years
Rotation period: 16.34 hours
Date discovered: 2002.6.18
Satellite: ?
Classification: TNO, KBO - Cubewano
Orbit
2002 MS4 currently 47.2 AU from the Sun and will come to perihelion around 2122.
How big is it?
2002 MS4 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
Mike Brown's automatically updated website lists it as a highly likely dwarf planet.
The Spitzer Space Telescope has estimated it to have a diameter of 726 ± 123 km.
Sunday 4 March 2012
(303775) 2005 QU182 - 14th Largest TNO? 4th Largest SDO?
2005 QU182 is a trans-Neptunian object and is possibly the 14th largest TNO and 4th largest SDO currently known.
Discovery
2005 QU182 is discovered on August 30, 2005 by Michael E. Brown, Chadwick A. Trujillo and David Lincoln Rabinowitz.
2005 QU182 has precovery images back to 1974.
Stats
Estimated Diameter: 730 km (530 - 1186 km)
Aphelion: 190.75 AU
Perihelion: 37.01 AU
Semi-major axis: 113.88 AU
Orbital Period: 1215 years
Rotation period: ? hours
Date discovered: 2005.8.30
Satellite: ?
Classification: TNO, SDO
Orbit
2005 QU182 takes over 1,200 years to orbit the Sun. Of the dwarf planets and known dwarf-planet candidates, only Sedna is known to have a longer orbit around the Sun.
2005 QU182 came to perihelion in 1971, and is currently 49 AU from the Sun.
How big is it?
2005 QU182 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
2005 QU182 has a bright absolute magnitude of 3.5. This qualifies it as one of the largest dwarf-planet candidates. As of August 2011, Mike Brown lists it as highly likely a dwarf planet.
Discovery
2005 QU182 is discovered on August 30, 2005 by Michael E. Brown, Chadwick A. Trujillo and David Lincoln Rabinowitz.
2005 QU182 has precovery images back to 1974.
Stats
Estimated Diameter: 730 km (530 - 1186 km)
Aphelion: 190.75 AU
Perihelion: 37.01 AU
Semi-major axis: 113.88 AU
Orbital Period: 1215 years
Rotation period: ? hours
Date discovered: 2005.8.30
Satellite: ?
Classification: TNO, SDO
Orbit
2005 QU182 takes over 1,200 years to orbit the Sun. Of the dwarf planets and known dwarf-planet candidates, only Sedna is known to have a longer orbit around the Sun.
2005 QU182 came to perihelion in 1971, and is currently 49 AU from the Sun.
How big is it?
2005 QU182 is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the TNO. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
Dwarf-planet candidate
2005 QU182 has a bright absolute magnitude of 3.5. This qualifies it as one of the largest dwarf-planet candidates. As of August 2011, Mike Brown lists it as highly likely a dwarf planet.
(55565) 2002 AW197 - 13th Largest TNO? 5th Largest Cubewano ?
2002 AW197 is a large trans-Neptunian object. 2002 AW197 is possibly the 13th largest TNO and 5th largest Cubewano currently known.
Discovery
2002 AW197 is discovered on January 10, 2002 by Michael E. Brown, Chadwick A. Trujillo, Eleanor F. Helin, Michael Hicks, Kenneth J. Lawrence and Steven H. Pravdo at Palomar Observatory.
Stats
Estimated Diameter: 734 km (626 - 850 km)
Aphelion: 53.53 AU
Perihelion: 41.07 AU
Semi-major axis: 47.28 AU
Orbital Period: 325.15 years
Rotation period: 8.86 hours
Date discovered: 2002.1.10
Satellite: ?
Classification: TNO, KBO - Cubewano
Orbit
2002 AW197 is currently 46.2 AU from the Sun and will come to perihelion around 2079.
Surface
ESO analysis of 2002 AW197 spectra reveals a strong red slope and no presence of water ice.
Dwarf-planet candidate
Measurements with the Spitzer Space Telescope have confirmed 2002 AW197 as a reliable dwarf-planet candidate, although it has not been officially classified as such by the IAU. Light-curve-amplitude analysis shows only small deviations, which suggests that 2002 AW197 is a spheroid with small albedo spots.
Discovery
2002 AW197 is discovered on January 10, 2002 by Michael E. Brown, Chadwick A. Trujillo, Eleanor F. Helin, Michael Hicks, Kenneth J. Lawrence and Steven H. Pravdo at Palomar Observatory.
Stats
Estimated Diameter: 734 km (626 - 850 km)
Aphelion: 53.53 AU
Perihelion: 41.07 AU
Semi-major axis: 47.28 AU
Orbital Period: 325.15 years
Rotation period: 8.86 hours
Date discovered: 2002.1.10
Satellite: ?
Classification: TNO, KBO - Cubewano
Orbit
2002 AW197 is currently 46.2 AU from the Sun and will come to perihelion around 2079.
Surface
ESO analysis of 2002 AW197 spectra reveals a strong red slope and no presence of water ice.
Dwarf-planet candidate
Measurements with the Spitzer Space Telescope have confirmed 2002 AW197 as a reliable dwarf-planet candidate, although it has not been officially classified as such by the IAU. Light-curve-amplitude analysis shows only small deviations, which suggests that 2002 AW197 is a spheroid with small albedo spots.
Saturday 3 March 2012
11th Largest Moon of Neptune - Sao (10th Moon outwards from Neptune)
Sao is a prograde irregular satellite of Neptune.
Sao is the 11th overall largest satellite of Neptune and 68th largest moon in the Solar System currently known.
Discovery
Matthew J. Holman, Harvard-Smithsonian Center for Astrophysics (CfA); John J. Kavelaars, National Research Council of Canada; T. Grav, University of Oslo and CfA; and W. Fraser and Dan Milisavljevic, McMaster University, reported the discovery of three satellites of Neptune on CCD images obtained in 14 August 2002 with the 4-m Blanco telescope at Cerro Tololo.
One of the satellites was Sao.
Naming
The moon was given the temporary designation S/2002 N2.
Sao the moon is named after one of the Nereids, the fifty daughters of Nereus and Doris. Sao was associated with sailing and is referred to as "The rescuer" or "Safety".
Stats
Diameter (mean): 44 km
Semi-major axis: 22,228,000 km
Orbital Period: 2912.72 days
Rotation Period: ?
Orbit
Sao follows an exceptionally inclined and moderately eccentric orbit in relation to other irregular satellites of Neptune.
Sao is in so-called Kozai resonance, i.e. its inclination and eccentricity are coupled (the inclination of the orbit decreases while eccentricity increases and vice versa).
Physical characteristics
Little is known about Sao.
Sao is about 44 kilometers in diameter (assuming an albedo of 0.04).
Sao is the 11th overall largest satellite of Neptune and 68th largest moon in the Solar System currently known.
Discovery
Matthew J. Holman, Harvard-Smithsonian Center for Astrophysics (CfA); John J. Kavelaars, National Research Council of Canada; T. Grav, University of Oslo and CfA; and W. Fraser and Dan Milisavljevic, McMaster University, reported the discovery of three satellites of Neptune on CCD images obtained in 14 August 2002 with the 4-m Blanco telescope at Cerro Tololo.
One of the satellites was Sao.
Naming
The moon was given the temporary designation S/2002 N2.
Sao the moon is named after one of the Nereids, the fifty daughters of Nereus and Doris. Sao was associated with sailing and is referred to as "The rescuer" or "Safety".
Stats
Diameter (mean): 44 km
Semi-major axis: 22,228,000 km
Orbital Period: 2912.72 days
Rotation Period: ?
Orbit
Sao follows an exceptionally inclined and moderately eccentric orbit in relation to other irregular satellites of Neptune.
Sao is in so-called Kozai resonance, i.e. its inclination and eccentricity are coupled (the inclination of the orbit decreases while eccentricity increases and vice versa).
Physical characteristics
Little is known about Sao.
Sao is about 44 kilometers in diameter (assuming an albedo of 0.04).
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