Discovery | |
---|---|
Discovered by | Norman Robert Pogson |
Discovery date | May 16, 1866 |
Designations | |
(87) Sylvia | |
Pronunciation | /ˈsɪlviə/ SIL-vee-ə [1] |
Named after | Rhea Silvia |
A909 GA | |
main belt ·(outside core) Sylvia · Cybele | |
Adjectives | Sylvian ( /ˈsɪlviən/ SIL-vee-ən) |
Orbital characteristics [2] | |
Epoch July 01, 2021 (JD 2459396.5, heliocentric) | |
Aphelion | 3.81 AU (560 Gm) |
Perihelion | 3.15 AU (480 Gm) |
3.48 AU (520 Gm) | |
Eccentricity | 0.094 |
6.5 a (2372 d) | |
Average orbital speed | 15.94 km/s[ citation needed ] |
213° | |
0° 9m 6.48s / day | |
Inclination | 10.9° |
73° | |
263° | |
Known satellites | 2 |
Physical characteristics [3] | |
Dimensions | (363 × 249 × 191) ±5 km (MPCD) or (374 × 248 × 194) ±5 km (ADAM) |
Mean diameter | 271±5 km(MPCD) or 274±5 km(ADAM) |
Volume | (10.5±0.2)×107 km3(MPCD) or (10.8±0.2)×107 km3(ADAM) |
Mass | (14.76±0.06)×1018 kg [4] (14.6±0.1)×1018 kg [5] |
Mean density | 1.378±0.045 g/cm3[ citation needed ] |
0.2160 d (5.183641±0.000039 h) | |
North pole right ascension | 14.3°±5° |
North pole declination | +83.5°±5° |
Pole ecliptic latitude | +64.2°±5° |
Pole ecliptic longitude | 75.3°±5° |
0.0435 [6] | |
X [7] | |
6.94 | |
Sylvia (minor planet designation: 87 Sylvia) is one of the largest asteroids (approximately tied for 7th place, to within measurement uncertainties). It is the parent body of the Sylvia family and member of Cybele group located beyond the main asteroid belt (see minor-planet groups). Sylvia was the first asteroid known to possess more than one moon.
Sylvia was discovered by N. R. Pogson on May 16, 1866, from Madras (Chennai), India. [8] Antonio Paluzie-Borrell, writing in Paul Herget's The Names of the Minor Planets (1955), mistakenly states that the name honors Sylvie Petiaux-Hugo Flammarion, the first wife of astronomer Camille Flammarion. In fact, in the article announcing the discovery of the asteroid, Pogson explained that he selected the name in reference to Rhea Silvia, mother of Romulus and Remus (MNRAS, 1866).
Sylvia is very dark in color and probably has a primitive composition, though with some internal differentiation. The discovery of its moons made possible an accurate measurement of the asteroid's mass, density and mass distribution. Its density is low (around 1.4 times the density of water), indicating that the asteroid is porous; best-fit models estimate it had an original composition by volume of 35% rock, 13% ice and 52% internal voids, and that today it consists of a pristine anhydrous outer layer, and a differentiated interior, with meltwater having percolated inward so that the porosity of the rock is filled with ice out to a radius of about 46 km, then ice-free porous rock out to about 104 km. [3]
Sylvia is a fairly fast rotator, turning about its axis every 5.2 hours, giving it an equatorial rotation velocity of about 65 m/s, almost half the escape velocity.
Sylvia's shape is flattened and elongated (a/b ≈ 1.45 ; a/c ≈ 1.84) and somewhat irregular. However, its surface has not been imaged well enough for individual features to be resolved.
Sylvia has two orbiting satellites. They have been named (87) Sylvia I Romulus and (87) Sylvia II Remus, after Romulus and Remus, the children of the mythological Rhea Silvia.
Romulus, the first moon, was discovered on February 18, 2001, from the Keck II telescope by Michael E. Brown and Jean-Luc Margot. Remus, the second moon, was discovered over three years later on August 9, 2004, by Franck Marchis of UC Berkeley, and Pascal Descamps, Daniel Hestroffer, and Jérôme Berthier of the Observatoire de Paris, France.
The orbital properties of the satellites are listed in this table. [3] [9] The orbital planes of both satellites and the equatorial plane of the primary asteroid are all well-aligned. Diameters are estimates based on the assumption that the moons have the same albedo as their primary.
Name | Mass [kg] | Diameter [km] | Semi-major axis [km] | Orbital period [days] | Eccentricity | Inclination [°] |
---|---|---|---|---|---|---|
Remus | (0.8±0.2)×1015 | 10+17 −6 | 694.2±0.1 | 1.3570±0.0003 | 0.005+0.010 −0.002 | 8.7±1.8 |
Romulus | (1.4±0.4)×1015 | 15+10 −6 | 1340.6±0.4 | 3.64126±0.00002 | 0.000+0.003 −0.000 | 7.4±0.5 |
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body. Natural satellites are colloquially referred to as moons, a derivation from the Moon of Earth.
A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. As of January 2022, there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons are important because the determination of their orbits provides estimates on the mass and density of the primary, allowing insights into their physical properties that are generally not otherwise accessible.
624 Hektor is the largest Jupiter trojan and the namesake of the Hektor family, with a highly elongated shape equivalent in volume to a sphere of approximately 225 to 250 kilometers diameter. It was discovered on 10 February 1907, by astronomer August Kopff at Heidelberg Observatory in southwest Germany, and named after the Trojan prince Hector, from Greek mythology. It has one small 12-kilometer sized satellite, Skamandrios, discovered in 2006.
Eugenia is a large asteroid of the asteroid belt. It is famed as one of the first asteroids to be found to have a moon orbiting it. It was also the second triple asteroid to be discovered, after 87 Sylvia.
216 Kleopatra is a large M-type asteroid with a mean diameter of 120 kilometers and is noted for its elongate bone or dumbbell shape. It was discovered on 10 April 1880 by Austrian astronomer Johann Palisa at the Austrian Naval Pola Observatory, in what is now Pula, Croatia, and was named after Cleopatra, the famous Egyptian queen. It has two small minor-planet moons which were discovered in 2008 and later named Alexhelios and Cleoselene.
762 Pulcova is a main-belt asteroid. It was discovered by Grigoriy N. Neujmin in 1913, and is named after Pulkovo Observatory, near Saint Petersburg. Pulcova is 137 km in diameter, and is a C-type asteroid, which means that it is dark in colouring with a carbonate composition.
Harpalyke, also known as Jupiter XXII, is a retrograde irregular satellite of Jupiter. It was discovered by a team of astronomers from the University of Hawaii led by Scott S. Sheppard in 2000, and given the temporary designation S/2000 J 5. In August 2003, the moon was named after Harpalyke, the incestuous daughter of Clymenus, who in some accounts was also a lover of Zeus (Jupiter).
Camilla is one of the largest asteroids from the outermost edge of the asteroid belt, approximately 250 kilometers in diameter. It is a member of the Sylvia family and located within the Cybele group. It was discovered on 17 November 1868, by English astronomer Norman Pogson at Madras Observatory, India, and named after Camilla, Queen of the Volsci in Roman mythology. The X-type asteroid is a rare trinary asteroid with two minor-planet moons discovered in 2001 and 2016, respectively. It is elongated in shape and has a short rotation period of 4.8 hours.
Hermione is a very large binary asteroid discovered in 1872. It orbits in the Cybele group in the far outer asteroid belt. As an asteroid of the dark C spectral type, it is probably composed of carbonaceous materials. In 2002, a small moon was found to be orbiting Hermione.
Kalliope is a large M-type asteroid from the asteroid belt discovered by J. R. Hind on 16 November 1852. It is named after Calliope, the Greek Muse of epic poetry. It is orbited by a small moon named Linus.
5261 Eureka is the first Mars trojan discovered. It was discovered by David H. Levy and Henry Holt at Palomar Observatory on 20 June 1990. It trails Mars (at the L5 point) at a distance varying by only 0.3 AU during each revolution (with a secular trend superimposed, changing the distance from 1.5–1.8 AU around 1850 to 1.3–1.6 AU around 2400). Minimum distances from Earth, Venus, and Jupiter, are 0.5, 0.8, and 3.5 AU, respectively.
Huenna is a large asteroid orbiting in the asteroid belt. It is part of the Themis family, and thus a C-type asteroid and consequently composed mainly of carbonaceous material.
702 Alauda, provisional designation 1910 KQ, is a carbonaceous asteroid and binary system from the outer asteroid belt, approximately 190 kilometers in diameter. It is the parent body of the Alauda family. Discovered in 1910 by German astronomer Joseph Helffrich at Heidelberg Observatory, it was named after the lark (alauda). Its small moon, named Pichi üñëm, was discovered in 2007.
854 Frostia is a main-belt asteroid orbiting the Sun. It was discovered in 1916 by Sergei Ivanovich Belyavsky from Simeiz Observatory in Crimea and is named after Edwin Brant Frost, an American astronomer. This asteroid measures approximately 8.4 km (5.2 mi) in diameter.
3749 Balam is a stony Flora asteroid and rare trinary system orbiting in the inner regions of asteroid belt. It also forms a secured asteroid pair with sub-kilometer sized asteroid (312497) 2009 BR60. Balam was discovered on 24 January 1982, by American astronomer Edward Bowell at Lowell's Anderson Mesa Station near Flagstaff, Arizona, and received the prov. designation 1982 BG1. It was named after Canadian astronomer David Balam. Balam measures approximately 4.1 kilometers (2.5 miles) in diameter. Its two minor-planet moons have an estimated diameter of 1.66 and 1.84 kilometers, respectively.
Linus, formal designation (22) Kalliope I Linus, is an asteroid moon that orbits the large M-type asteroid 22 Kalliope. It was discovered on August 29, 2001, by astronomers Jean-Luc Margot and Michael E. Brown with the Keck telescope, in Hawaii. Another team also detected the moon with the Canada-France-Hawaii Telescope on September 2, 2001. Both telescopes are on Mauna Kea. It received the provisional designation S/2001 (22) 1, until it was named. The naming proposal appeared in the discovery paper and was approved by the International Astronomical Union in July 2003. Although the naming proposal referred to the mythological Linus, son of the muse Calliope and the inventor of melody and rhythm, the name was also meant to honor Linus Torvalds, inventor of the Linux operating system kernel, and Linus van Pelt, a character in the Peanuts comic strip.
Romulus is the outer and larger moon of the main-belt asteroid 87 Sylvia. It follows an almost-circular and close-to-equatorial orbit around the asteroid. In this respect it is similar to the other Sylvian moon Remus.
Remus is the inner and smaller moon of the main-belt asteroid 87 Sylvia. It follows an almost-circular and close-to-equatorial orbit around the parent asteroid. In this respect it is similar to the other Sylvian moon Romulus.
(26308) 1998 SM165 is a resonant trans-Neptunian object and binary system from the Kuiper belt in the outermost regions of the Solar System. It was discovered on 16 September 1998, by American astronomer Nichole Danzl at the Kitt Peak National Observatory in Arizona. It is classified as a twotino and measures approximately 280 kilometers in diameter. Its minor-planet moon was discovered in 2001.
(185851) 2000 DP107 is a sub-kilometer sized asteroid, classified as potentially hazardous asteroid and near-Earth object of the Apollo group that is notable because it provided evidence for binary asteroids in the near-Earth population. The PROCYON probe developed by JAXA and the University of Tokyo was intended to flyby this asteroid before its ion thruster failed and could not be restarted.