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Minor planet moon

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A minor planet moon is a minor planet that orbits another minor planet as its natural satellite. It is thought that many asteroids and Kuiper belt objects may possess moons, in some cases quite substantial in size. Discoveries of asteroid moons (and binary objects, in general) are important because the determination of their orbits provides estimates on the mass and density of the primary, allowing insights of their physical properties that is generally not otherwise possible.

TerminologyEdit

In addition to the terms satellite and moon, the term binary is sometimes used for minor planets with moons (or triple for minor planets with two moons). If one object is much bigger it is usually referred to as the primary and its companion as secondary. The term double asteroid is sometimes used for systems in which the asteroid and its moon are roughly the same size, while binary tends to be used independently from the relative sizes of the components.

Discovery milestonesEdit

As early as 1978, following a stellar occultation, 532 Herculina had been suggested to have a moon and there were reports of other asteroids having companions (usually referred to as satellites) in the following years. A letter in Sky & Telescope magazine at this time pointed to pairs of large craters (e.g. the Clearwater Lakes in Quebec) also suggesting asteroids having companions. However, it was not until 1993 that the first asteroid moon was confirmed when the Galileo probe discovered Dactyl orbiting 243 Ida. The second was discovered around 45 Eugenia in 1998. The first Trans-Neptunian binary, 1998 WW31 was optically resolved in 2002.[1]

As of September 2008, 104 asteroid moons had been discovered, 60 in the main belt, 2 orbiting Trojan asteroids, 42 near-Earth objects and Mars-crossers. There were at that time also 58 Trans-Neptunian moons. In 2005, the asteroid 87 Sylvia was discovered to have two moons, making it the first known triple asteroid. This was followed by the discovery of a second moon orbiting 45 Eugenia. Also in 2005, the KBO Haumea was discovered to have two moons, making it the second KBO after Pluto known to have more than one moon.[2]

An example of a double asteroid is 90 Antiope, where two roughly equal-sized components orbit the common centre of gravity. 617 Patroclus and its same-sized companion Menoetius is the only known binary system in the Trojan population.

CommonalityEdit

The data about the populations of binary objects are still patchy. In addition to the inevitable observational bias (dependence on the distance from Earth, size, albedo and separation of the components) the frequency appears to be different among different categories of objects. Among asteroids, an estimated 2% would have satellites. Among trans-Neptunian objects (TNO), an estimated 11% are believed to be binary or multiple objects, but three of the four known large TNO (75%) have at least one satellite.

More than 20 binaries are known in each of the main groupings: Near Earth asteroids, Main belt asteroids, and Trans-Neptunians, not including numerous claims based solely on the light curve variation.

No binaries have been found so far among Centaurs with semi-major axis smaller than Neptune.[3] However, using an extended definition of Centaurs, as the objects on instable orbits with the perihelion inside the orbit of Neptune, the first binary Centaur 42355_Typhon (previously known as 2002 CR46) was identified in 2006.[4]

OriginEdit

The origin of asteroid moons is not currently known with certainty, and a variety of theories exist. A widely accepted theory is that asteroid moons are formed from debris knocked off of the primary asteroid by an impact. Other pairings may be formed when a small object is captured by the gravity of a larger one.

Formation by collision is constrained by the angular momentum of components i.e. by the masses and their separation. Close binaries fit this model (e.g. Pluto/Charon). Distant binaries however, with components of comparable size, are unlikely to have followed this scenario, unless considerable mass has been lost in the event.

The distances of the components for the known binaries vary from a few hundreds of kilometres (243 Ida, 3749 Balam) to more than 3000 km (379 Huenna) for the asteroids. Among TNOs, the known separations vary from 3,000 to 50,000 km.[3]

PopulationsEdit

What is "typical" for a binary asteroid system tends to depend on its location in the Solar System (presumably because of different modes of origin and lifetimes of such systems in different populations of minor planets).[5]

  • Among Near-Earth Asteroids, satellites tend to orbit at distances of the order of 3-7 primary radii, and have diameters two to several times smaller than the primary. Since these binaries are all inner-planet crossers, it is thought that tidal stresses that occurred when the parent object passed close to a planet may be responsible for the formation of many of them, although collisions are thought to also be a factor in the creation of these satellites.
  • Among main belt asteroids, the satellites are usually much smaller than the primary (a notable exception being 90 Antiope), and orbit around 10 primary radii away. Many of the binary systems here are members of asteroid families, and a good proportion of satellites are expected to be fragments of a parent body whose disruption after an asteroid collision produced both the primary and satellite.
  • Among Trans-Neptunian Objects, it is common for the two orbiting components to be of comparable size, and for the semi-major axis of their orbits to be much larger − about 100 to 1000 primary radii. A significant proportion of these binaries are expected to be primordial.

Dwarf planetsEdit

Among the dwarf planets, it is 90 percent certain that Ceres has no moons larger than 1 km in size, assuming that they would have the same albedo as Ceres itself.[6] Pluto has three moons. Its largest moon Charon, named after the ferryman who took souls across the River Styx, is more than half as large as Pluto itself, and large enough to orbit a point outside Pluto's surface. In effect, each orbits the other, forming a binary system informally referred to as a double-dwarf-planet. Pluto's two other moons, Nix and Hydra, are far smaller and orbit the Pluto–Charon system. Makemake has no known moons. A satellite having 1% Makemake's brightness would have been detected if it had been located at an angular distance from Makemake farther than 0.4 arcseconds (0.0001 degrees).[7] Eris has one known moon, Dysnomia. Its radius, based on its brightness, is estimated to be 50 to 125 km.[8] Haumea has two small moons with radiuses estimated around 155 km (Hiʻiaka) and 85 km (Namaka).

List of minor planet moonsEdit

Near Earth objectsEdit

Name Type Diameter (km)
(or dimensions)
Name of moon Diameter of moon (km)
(or dimensions)
Separation (km)
1862 Apollo Apollo 1.7 S/2005 (1862) 1 0.08 3
3671 Dionysus Amor 1.5 S/1997 (3671) 1 0.4 2.2
5381 Sekhmet Aten 1 S/2003 (5381) 1 0.3 1.54 ± 0.12
7088 Ishtar Amor 1.5? S/2006 (7088) 1  ?  ?
(31345) 1998 PG Amor 0.9 S/2001 (31345) 1 0.3 1.5
(35107) 1991 VH Apollo 1.2 S/2001 (35107) 1 0.5 3.2
65803 Didymos Amor 0.8 S/2003 (65803) 1 0.15 ± 0.05 1.1
(66063) 1998 RO1 Aten 0.9 S/2001 (66063) 1 0.36 0.8
(66391) 1999 KW4 Aten 1.2 S/2001 (66391) 1 > 0.36 2.6
69230 Hermes Apollo 0.4 S/2003 (69230) 1 0.4 1
(85938) 1999 DJ4 Apollo 0.7 S/2004 (85938) 1 0.35 1.5
(88710) 2001 SL9 Apollo 1 S/2001 (88710) 1 0.31 1.8
(137170) 1999 HF1 Aten 3.5 S/1999 (137170) 1 0.8 7.0
1990 OS Apollo 0.3 S/2003 (1990 OS) 1 0.045 0.6
1994 CC  ? 0.7  ? 2 both ~0.05  ?
1994 AW1 Amor 0.9 Template:Mpm- 0.5 2.1
1994 XD Apollo 1? S/2005 (1994 XD) 1  ?  ?
1996 FG3 Apollo 1.4 Template:Mpm- 0.43 2.4
1998 ST27 Aten 0.8 Template:Mpm- 0.12 4.5 ± 0.5
2000 DP107 Apollo 0.80 (± 0.16) Template:Mpm- 0.30 (± 0.15) 2.622 ± 0.162
2000 UG11 Apollo 0.23 ± 0.06 Template:Mpm- 0.10 0.337 ± 0.013
2002 BM26 Amor 0.6 Template:Mpm- 0.1 1.5
2002 CE26 Apollo 3 Template:Mpm- 0.2 5
2002 KK8 Amor 0.5 Template:Mpm- 0.1  ?
2003 SS84 Apollo 0.12 Template:Mpm- 0.06 0.3?
2003 YT1 Apollo 1 Template:Mpm- 0.18 ~2.7
2004 DC Apollo 0.3 S/2006 (2004 DC) 1  ?  ?
2005 AB Amor 1.2? S/2005 (2005 AB) 1 0.3 2.5?
2005 NB7 Apollo 0.5 ± 0.1 Template:Mpm- 0.2 ± 0.1 ≥ 0.6
2006 GY2 Apollo 0.45 Template:Mpm-  ?  ?

Mars crossersEdit

Name Diameter (km)
(or dimensions)
Name of moon Diameter of moon (km)
(or dimensions)
Separation (km)
1139 Atami 7 S/2005 (1139) 1 7  ?
2044 Wirt 8? S/2006 (2044) 1  ?  ?
(5407) 1992 AX 4 S/2001 (5407) 1 1.2 6.8
(34706) 2001 OP83 4? S/2005 (34706) 1 1? 8?
(114319) 2002 XD58 3? S/2005 (114319) 1  ?  ?

Main belt asteroidsEdit

Name Diameter (km)
(or dimensions)
Name of moon Diameter of moon (km)
(or dimensions)
Separation (km)
22 Kalliope (215×180×150) Linus 38 ± 6 1,065 ± 8
45 Eugenia (305×220×145) Petit-Prince (Eugenia I) 13 ± 1 1,184 ± 12
S/2004 (45) 1 ~6 ~700(?)
87 Sylvia (385×265×230) Remus (Sylvia II) 7 ± 2 706 ± 5
Romulus (Sylvia I) 18 ± 4 1,356 ± 5
90 Antiope 110±16 S/2000 (90) 1 110 ± 16 170 ± 1
107 Camilla (285×205×170) ± 20 S/2001 (107) 1 11 ± 2 1,235 ± 16
121 Hermione (254×125) S/2002 (121) 1 12 ± 4 768 ± 11
130 Elektra (215×155) S/2003 (130) 1 6 ± 2 1,252 ± 30
243 Ida (59.8×25.4×18.6) Dactyl (Ida I) (1.6×1.4×1.2) 108
283 Emma 148.1 ± 4.6 S/2003 (283) 1 12 596 ± 3
379 Huenna 92.3 ± 1.7 S/2003 (379) 1 7 3,400 ± 11
762 Pulcova 137.1 ± 3.2 S/2000 (762) 1 20 810
809 Lundia ~7 - 10 S/2005 (809) 1 ~7 - 10 ~10 – 20
854 Frostia 13.7 ± 5.6 S/2004 (854) 1 10 ~25
1089 Tama 12.9 S/2003 (1089) 1 9 20
1313 Berna 11 S/2004 (1313) 1 11 35
1509 Esclangona 12 S/2003 (1509) 1 4 140
1717 Arlon 9? S/2006 (1717) 1  ? 18?
2006 Polonskaya 10 S/2005 (2006) 1  ?  ?
2478 Tokai 10? S/2007 (2478) 1  ?  ?
2486 Metsähovi 12? S/2007 (2486) 1  ?  ?
2754 Efimov 7? S/2006 (2754) 1  ? 12?
3073 Kursk 8? S/2007 (3073) 1  ?  ?
3309 Brorfelde 6? S/2005 (3309) 1  ?  ?
3703 Volkonskaya 3 S/2003 (3703) 1 1.2  ?
3749 Balam 7 S/2002 (3749) 1 1.5 310 ± 20
3782 Celle 6 S/2003 (3782) 1 2.5 30
3982 Kastel  ? S/2005 (3982) 1  ?  ?
4029 Bridges 10 S/2006 (4029) 1  ?  ?
4492 Debussy 10 S/2004 (4492) 1  ? 25
4674 Pauling 8 S/2004 (4674) 1 2.5 250
4786 Tatianina 8? S/2006 (4786) 1  ?  ?
(5477) 1989 UH2 ~7 S/2005 (5477) 1 2.5 15
5905 Johnson 5 S/2005 (5905) 1 2  ?
6084 Bascom 9? S/2006 (6084) 1 3.5? 32?
6244 Okamoto 7? S/2006 (6244) 1 1.7? 15?
9069 Hovland 3 S/2004 (9069) 1 0.9  ?
9260 Edwardolson ~4 S/2005 (9260) 1  ?  ?
9617 Grahamchapman 5? S/2006 (9617) 1 1.4?  ?
11264 Claudiomaccone 4 S/2003 (11264) 1 1.2  ?
(17246) 2000 GL74 4.5 S/2004 (17246) 1 2 ~230
(17260) 2000 JQ58 6? S/2006 (17260) 1 1.5? 10?
(22899) 1999 TO14 4.5 S/2003 (22899) 1 1.5 ~170
(76818) 2000 RG79 3.6 S/2005 (76818) 1 1.1  ?

Jupiter trojansEdit

Name Diameter (km)
(or dimensions)
Name of moon Diameter of moon (km)
(or dimensions)
Separation (km)
617 Patroclus 121.8 ± 3.2 Menoetius (Patroclus I) 112.6 ± 3.2 685 ± 40
624 Hektor (363×207) S/2006 (624) 1 15 1,000?

Trans-Neptunian objectsEdit

Name Type Diameter (km)
(or dimensions)
Name of moon Diameter of moon (km)
(or dimensions)
Separation (km)
Pluto Plutino 2306±20 Charon (Pluto I) 1207±3 19,571±4
Nix (Pluto II) 44-130 48,675±120
Hydra (Pluto III) 44-130 64,780±90
(26308) 1998 SM165 Plutino 221? S/2001 (26308) 1 88 11,310 ± 110
42355 Typhon SDO 134 Echidna (Typhon I) 78 1,300?
(47171) 1999 TC36 Plutino 375 ± 50 S/2001 (47171) 1 140 7,640 ± 460
(48639) 1995 TL8 SDO 352 S/2005 (48639) 1 161 420
50000 Quaoar Cubewano 1260 S/2007 (50000) 1 96?  ?
(55637) 2002 UX25 Cubewano 649 S/2007 (55637) 1 205  ?
58534 Logos Cubewano 80 Zoe (Logos I) 66 8,010 ± 80
(60458) 2000 CM114 SDO 150? S/2006 (60458) 1 119? 2,200?
(60621) 2000 FE8 2:5 resonance 151? S/2007 (60621) 1 115? 1,200
65489 Ceto SDO 172 Phorcys (Ceto I) 134 1,840
66652 Borasisi Cubewano 166 Pabu (Borasisi I) 137 4,660 ± 170
(79360) 1997 CS29 Cubewano 305 S/2005 (79360) 1 292 2300
(80806) 2000 CM105 Cubewano 224 S/2005 (80806) 1 129 2700
(82075) 2000 YW134 SDO 431 S/2005 (82075) 1 237 1900
88611 Teharonhiawako Cubewano 176 ± 20 Sawiskera (Teharonhiawako I) 122 ± 14 27,300 ± 343
90482 Orcus Plutino 946 S/2007 (90482) 1 262 ± 170 8,700
(119979) 2002 WC19 1:2 resonance 420? S/2007 (119979) 1  ?  ?
(120347) 2004 SB60 Cubewano 580? S/2006 (120347) 1  ? 3,500?
(123509) 2000 WK183 Cubewano 221? S/2007 (123509) 1  ?  ?
(134860) 2000 OJ67 Cubewano 253? S/2003 (134860) 1 175? 2,300?
136108 Haumea Cubewano 1400 Hiʻiaka (136108 Haumea I) 310 49,500 ± 400
Namaka (136108 Haumea II) 170 39,300
Eris SDO 2,800 Dysnomia (Eris I) 150-250 30,000-36,000
(139775) 2001 QG298 Plutino 171? S/2004 (139775) 1 171? 240?
(148780) Altjira Cubewano 340? S/2007 (148780) 1 246? 5,800?
1998 WW31 Cubewano 133 ± 15 S/2000 (1998 WW31) 1 110 ± 12 22,300 ± 800
1999 OJ4 Cubewano? 168 Template:Mpm- 93 2,200
1999 RT214 Cubewano 120? Template:Mpm-  ? 3,300?
2000 CF105 Cubewano 170 Template:Mpm- 120 23,000
2000 CQ114 Cubewano 164? Template:Mpm- 133 5,880 ± 200
2000 QL251 Cubewano? 176? Template:Mpm- 176? 7,000?
2001 FL185 Cubewano 144? Template:Mpm- 100? 1,900?
2001 QY297 Cubewano 282? Template:Mpm- 233? 2,800?
2001 RZ143 Cubewano 201? Template:Mpm- 192? 1,400?
2001 QC298 Cubewano 189 Template:Mpm- 155 3,690 ± 70
2001 QW322 Cubewano 86 Template:Mpm- 86 ~130,000
2002 GZ31 SDO 187? Template:Mpm- 118? ~2,060 ± 270
2003 AZ84 Plutino 686 +99/-96 Template:Mpm- 68 ± 20 7,200
2003 QW111 Plutino 265? Template:Mpm-  ? 10,000?
2003 QY90 SDO 196 Template:Mpm- 178 10,000
2003 UN284 Cubewano 127 Template:Mpm- 97 60,000
2004 PB108 Cubewano 210? Template:Mpm- 121? 5,400
2005 EO304 Cubewano 240 Template:Mpm-  ? 85,000

See alsoEdit

ReferencesEdit

  1. Chiang, E.; Lithwick, Y.; Buie, M.; Grundy, W.; Holman, M.; A Brief History of Trans-Neptunian Space, to appear in Protostars and Planets V (August 2006) Final preprint on arXiv
  2. [http://www.johnstonsarchive.net/astro/asteroidmoons.html
  3. 3.0 3.1 Noll, Keith S. "Solar System binaries", Asteroids, Comets, Meteors, Proceedings of the 229th Symposium of the IAU, Rio de Janeiro, 2005, Cambridge University Press, 2006., pp.301-318 Preprint
  4. K. Noll, H. Levison W. Grundy, D. Stephens (October 2006). "Discovery of a binary Centaur" (preprint). Icarus 184. 
  5. "T. Michałowski et al. (2004). "Eclipsing binary asteroid 90 Antiope". Astronomy & Astrophysics 423: 1159. doi:10.1051/0004-6361:20040449. 
  6. Bieryla, Allyson; Parker, J. W.. "Search for Satellites around Ceres". 2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #25.02; Bulletin of the American Astronomical Society 38: 933, http://adsabs.harvard.edu/abs/2006AAS...209.2502B. 
  7. M. E. Brown, M. A. van Dam, A. H. Bouchez, et al. (2006-03-01). "Satellites of the Largest Kuiper Belt Objects". The Astrophysical Journal 639: L43–L46. doi:10.1086/501524, http://adsabs.harvard.edu/abs/2006ApJ...639L..43B. 
  8. Mike Brown. "Dysnomia, the moon of Eris". Caltech. Retrieved on 2009-07-02.
  • Asteroids with Satellites web page, maintained up to date by W. Robert Johnston; and references therein. (last accessed 13-03-2007)
  • The VOBAD database a web page built and designed by F. Marchis and his collaborators (UC-Berkeley/SETI Institute) which contains the parameters of 169 multiple asteroid systems (last update May 9 2009)

External linksEdit

bg:Астероиден спътник

ca:Satèl·lit asteroidal cs:Asteroidní měsícit:Satellite asteroidale nl:Planetoïdemaannn:Asteroidemåne pl:Księżyc planetoidysimple:Asteroid moon sk:Mesiac planétky sl:Asteroidna luna sv:Asteroidmåne th:ดวงจันทร์บริวารดาวเคราะห์น้อย

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