Minor-planet moon
Template:Short description Template:See also Template:Use dmy dates Template:Multiple image
A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. Template:As of, there are 457 minor planets known or suspected to have moons.<ref name="Johnstonsarchive-list" /> Discoveries of minor-planet 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 into their physical properties that are generally not otherwise accessible.<ref name="SwRI-2000" />
Several of the moons are quite large compared to their primaries: 90 Antiope, Mors–Somnus and Sila–Nunam (95%), Patroclus–Menoetius, Altjira and Lempo–Hiisi (90%, with Lempo–Paha at 50%). The largest known minor-planet moon in absolute size is Pluto's largest moon Charon, which itself has about half the diameter of Pluto.
There are also several known ring systems around distant objects (see: Rings of Chariklo and Chiron).
TerminologyEdit
In addition to the terms satellite and moon, the term "binary" (binary minor planet) is sometimes used for minor planets with one moon, and "triple" for minor planets with two moons. If one object is much bigger it is referred to as the primary and its companion as the 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. When binary minor planets are similar in size, the Minor Planet Center (MPC) refers to them as "binary companions" instead of referring to the smaller body as a satellite.<ref name="IAU-list" /> A good example of a true binary is the 90 Antiope system, identified in August 2000.<ref name="Keck-Antiope" /> Very small satellites are often referred to as moonlets.<ref name="SwRI-2000" /><ref name="IAUC-8732" />
Discovery milestonesEdit
Prior to the era of the Hubble Space Telescope and space probes reaching the outer Solar System, attempts to detect satellites around asteroids were limited to optical observations from Earth. For example, in 1978, stellar occultation observations were claimed as evidence of a satellite for the asteroid to 532 Herculina.<ref name="Dunham-1978" /><ref name="Dunham-1977" /> However, later more-detailed imaging by the Hubble Telescope did not reveal a satellite, and the current consensus is that Herculina does not have a significant satellite.<ref name="Storrs-1999" /> There were other similar reports of asteroids having companions (usually referred to as satellites) in the following years. A letter by astronomer Thomas Hamilton in the Sky & Telescope magazine at this time pointed to apparently simultaneous impact craters on Earth (for example, the Clearwater Lakes in Quebec), suggesting that these craters were caused by pairs of gravitationally bound objects.<ref name="Hamilton-2014" />
In 2014, 130 Elektra was discovered to have three moons, making it the only discovered quadruple asteroid.
Also in 1978, Pluto's largest moon Charon was discovered; however, at the time Pluto was still considered to be one of the major planets.
In 1993, the first asteroid moon was confirmed when the Galileo probe discovered the small Dactyl orbiting 243 Ida in the asteroid belt. The second was discovered around 45 Eugenia in 1998.<ref name="Eugenia" /> In 2001, 617 Patroclus and its same-sized companion Menoetius became the first known binary asteroids in the Jupiter trojans.<ref name="IAUC-7741" /> The first trans-Neptunian binary after Pluto–Charon, Template:Mpl, was optically resolved in 2002.<ref name="Chiang-2006" />
Multiple systemsEdit
In 2005, the asteroid 87 Sylvia was discovered to have two satellites, making it the first known triple system (also called a triple minor planet or triple asteroid).<ref name="IAUC-8582" /> This was followed by the discovery of a second moon orbiting 45 Eugenia.<ref name=IAUC-8817 /> Also in 2005, the dwarf planet Template:Dp was discovered to have two moons, making it the second trans-Neptunian object after Pluto known to have more than one moon.<ref name="Marchis-homepage" /> Additionally, 216 Kleopatra<ref name="SETI" /> and 93 Minerva<ref name="Marchis-2009" /> were discovered to be triple asteroids in 2008 and 2009 respectively. There has been one discovered quadruple minor planet, that being 130 Elektra. Since the first few triple minor planets were discovered, more continue to be discovered. Template:Asof, the total number of known multiple systems among minor planets is 18 (including the Pluto and Haumea systems).<ref name="Johnstonsarchive-list"/>
The following table lists all satellites of multiple systems, starting with Pluto, which was unnumbered when its first moon was discovered in 1978. The highest known multiplicities are for Pluto (a sextuple system) and 130 Elektra (a quadruple system).
Parent body | Minor-planet moon | ||||
---|---|---|---|---|---|
Designation | Orbital class | Designation | Discovery date |
Announcement date |
Announcement of triple |
Pluto | Kuiper Belt | Charon | 1978/06/22 | 1978/07/07 | 2005/10/31 |
Nix | 2005/05/15 | 2005/10/31 | |||
Hydra | |||||
Kerberos | 2011/06/28 | 2013/07/02 | |||
Styx | 2012/06/26 | 2013/07/02 | |||
45 Eugenia | Asteroid belt | Petit-Prince | 1998/11/01 | 1999/03/20 | 2007/03/07 |
S/2004 (45) 1<ref name=IAUC8817>Template:Cite journal</ref> | 2004/02/14 | 2007/03/07 | |||
87 Sylvia | Asteroid belt | Romulus | 2001/02/18 | 2005/08/11 | 2005/08/11 |
Remus | 2004/08/09 | ||||
93 Minerva | Asteroid belt | Aegis | 2009/08/16 | 2013/12/17 | 2013/12/17 |
Gorgoneion | |||||
107 Camilla | Asteroid belt | citation | CitationClass=web
}}</ref>|| 2001/03/01 || 2001/03/19 || rowspan="2" | 2016/08/07 | ||
S/2016 (107) 1<ref name="iauc9282">Template:Cite journal</ref> | 2015/05/29 | 2016/08/07 | |||
130 Elektra | Asteroid belt | – | 2003/08/15 | 2003/08/17 | 2014/12/16 |
– | 2014/12/06 | 2014/12/16 | |||
– | 2014/12/09 | 2021/11/06 | |||
216 Kleopatra | Asteroid belt | Alexhelios | 2008/09/19 | 2011/02/18 | 2011/02/18 |
Cleoselene | |||||
2577 Litva | Mars-crosser | – | 2009/02/28 | 2009/03/11 | 2013/12/22 |
– | 2012/06/22 | 2013/12/22 | |||
3122 Florence | Amor | – | 2017/08/29 | 2017/09/01 | 2017/09/01 |
– | |||||
3749 Balam | Asteroid belt | – | 2002/02/08 | 2002/02/13 | 2008/03/12 |
– | 2007/07/15 | 2008/03/12 | |||
4666 Dietz | Asteroid belt | – | 2015/09/02 | 2015/10/?? | 2018/07/20 |
– | 2015/09/02 | 2018/07/20 | |||
6186 Zenon | Asteroid belt | – | 2017/01/01 | 2017/01/14 | 2017/01/14 |
– | |||||
47171 Lempo | Kuiper belt | Paha | 2001/12/08 | 2002/01/10 | 2009/10/?? |
Hiisi | 2009/10/?? | 2009/10/?? | |||
136108 Haumea | Kuiper belt | Hiʻiaka | 2005/01/26 | 2008/09/17 | 2008/09/17 |
Namaka | 2005/06/30 | ||||
Template:Mpl | Apollo | Beta (unofficial) | 2009/06/12 | 2009/06/19 | 2009/06/19 |
Gamma (unofficial) | |||||
Template:Mpl | Amor | Beta (unofficial) | 2008/02/12 | 2008/02/12 | 2008/02/12 |
Gamma (unofficial) | |||||
Template:Mpl | Amor | – | 2015/08/?? | 2015/08/22 | 2020/06/09 |
– | 2020/05/?? | 2020/06/09 | |||
Template:Mpl | Aten | – | 2001/10/07 | 2001/10/09 | 2024/10/11 |
– | 2024/10/?? | 2024/10/11 |
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 (TNOs), an estimated 11% are thought to be binary or multiple objects, and the majority of the large TNOs have at least one satellite, including all four IAU-listed dwarf planets.
More than 50 binaries are known in each of the main groupings: near-Earth asteroids, belt asteroids, and trans-Neptunian objects, not including numerous claims based solely on light-curve variation.
Two binaries have been found so far among centaurs with semi-major axes smaller than Neptune.<ref name="Noll-2005" /> Both are double ring systems around 2060 Chiron and 10199 Chariklo, discovered in 1993–2011 and 2013 respectively.
OriginEdit
The origin of minor-planet moons is not currently known with certainty, and a variety of hypotheses exist. One such model is that minor-planet moons are formed from debris knocked off the primary 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 the 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.<ref name="Noll-2005" />
Populations and classesEdit
What is "typical" for a binary 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).<ref name="Michalowski-2004" />
- 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.
- Pluto has five known moons. Its largest moon Charon has a radius of more than half that of Pluto, and is large enough to orbit a point outside Pluto's surface. In fact, each orbits the common barycenter between them, with Pluto's orbit entirely enclosed by Charon's; thus they form a binary system informally referred to as a double dwarf planet. Pluto's four other moons, Nix, Hydra, Kerberos, and Styx, are far smaller and orbit the Pluto–Charon system.
- Haumea has two moons with radii estimated around 155 km (Hiʻiaka) and 85 km (Namaka).
- Template:Dp has one known moon, S/2015 (136472) 1, estimated to be some Template:Convert in diameter.
- 47171 Lempo is a unique trans-Neptunian triple system: Lempo and its moon of roughly equal mass, Hiisi, form a close-proximity binary, separated by roughly 867 km. A second moon, Paha, orbits the Lempo–Hiisi binary at about 7411 km.
- Template:Dp has one known moon, Dysnomia. Its radius, based on its brightness, is estimated to be roughly between 150 and 350 km.<ref name="TNO-Cool-4" />
Template:Anchor ListEdit
Template:As of, there are 457 minor planets (systems) with 477 known companions.<ref name="Johnstonsarchive-list" /> The following table is a listing of the total number of these systems by orbital class:
# of Systems | Orbital class | Template:Nowrap | Multiple satellites |
---|---|---|---|
86 | Near-Earth objects | go to list | Three systems with two satellites: 3122 Florence, Template:Mpl, and Template:Mpl. |
31 | Mars-crossing asteroids | goto list | One system with two satellites: 2577 Litva. |
212 | Main-belt asteroids | go to list | Eight systems with two satellites: 45 Eugenia, 87 Sylvia, 93 Minerva, 107 Camilla, 216 Kleopatra, 3749 Balam, 4666 Dietz, 6186 Zenon; and one quadruple system with three satellites: 130 Elektra. |
6 | Jupiter trojans | go to list | – |
122 | Trans-Neptunian objects | go to list | Two systems with two satellites: 47171 Lempo and 136108 Haumea; one system with five satellites: 134340 Pluto.<ref name="Johnstonsarchive-list" /><ref name="Marchis-2008" /> |
Near-Earth objectsEdit
This is a list of near-Earth asteroids with companions.<ref name="Johnstonsarchive-list" /> Candidate binaries with an unconfirmed status are displayed on a dark background.<ref name="Johnstonsarchive-confirmed-vs-candidates" /> For an overview, see summary and introduction.
Mars crossersEdit
This is a list of Mars-crossing asteroids with companions.<ref name="Johnstonsarchive-list" /> Candidate binaries with an unconfirmed status are displayed on a dark background.<ref name="Johnstonsarchive-confirmed-vs-candidates" /> For an overview, see summary and introduction.
Template:Anchor Main-belt asteroidsEdit
This is a list of main-belt asteroids with companions.<ref name="Johnstonsarchive-list" /> Candidate binaries with an unconfirmed status are displayed on a dark background.<ref name="Johnstonsarchive-confirmed-vs-candidates" /> For an overview, see summary and introduction.
The following binaries are double asteroids, with similarly sized components, and a barycenter outside of the larger object. Template:Div col
- 90 Antiope – S/2000 (90) 1<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- 854 Frostia – undesignated
- 1313 Berna – undesignated
- 2478 Tokai – undesignated
- 3169 Ostro – undesignated
- 3749 Balam – S/2002 (3749) 1<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- 3905 Doppler – undesignated
- 4674 Pauling – S/2004 (4674) 1<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- 4951 Iwamoto – undesignated
- 5674 Wolff – undesignated
- 8474 Rettig – undesignated
- 17246 Christophedumas – S/2004 (17246) 1<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- Template:Mpl – undesignated
Template:Div col end In addition, these bodies might be double asteroids, but due to errors in their size and orbit, it is uncertain. Template:Div col
- 809 Lundia – undesignated
- 1089 Tama – undesignated
- 1509 Esclangona – S/2003 (1509) 1<ref>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref>
- 4492 Debussy – undesignated
- 11264 Claudiomaccone – undesignated
- 22899 Alconrad – (22899) Alconrad I Juliekaibarreto<ref name="WGSBN-V4-14">Template:Cite journal</ref>
Jupiter trojansEdit
This is a list of Jupiter trojans with companions.<ref name="Johnstonsarchive-list" /> Candidate binaries with an unconfirmed status are displayed on a dark background.<ref name="Johnstonsarchive-confirmed-vs-candidates" /> For an overview, see summary and introduction.
System | Primary | Secondary | Refs | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Designation | Class | De (km) |
s/p-ratio | YOD | Dp (km) |
RTp (hours) |
Designation | YOD | Ds (km) |
as (km) |
Ps (hours) | ||
617 Patroclus | L5 | 145 | 0.924 | 1906 | 106 | 102.79 | Menoetius Template:Small | 2001 | 98 | 680 | 102.792 | Template:JA-BIN Template:JPL Template:LoMP Template:LCDB | |
624 Hektor | L4 | 250 | 0.048 | 1907 | 184 | 6.921 | Skamandrios Template:Small | 2006 | 12 | 957.5 | 71.162 | Template:JA-BIN Template:JPL Template:LoMP Template:LCDB | |
3548 Eurybates | L4 | 63.9 | 0.013 | 1973 | 63.9 | 8.711 | Queta Template:Small | 2018 | 0.8 | 2310 | 1982.4 | Template:JA-BIN Template:JPL Template:LoMP Template:LCDB | |
16974 Iphthime | L4 | 57.3 | 0.767 | 1998 | 45.5 | 78.9 | – | 2013 | 34.9 | 179 | 78.96 | Template:JA-BIN Template:JPL Template:LoMP Template:LCDB | |
17365 Thymbraeus | L5 | 42.6 | 0.843 | 1978 | 32.6 | 12.672 | – | 2005 | 27.5 | 43 | 12.672 | Template:JA-BIN Template:JPL Template:LoMP Template:LCDB | |
29314 Eurydamas | L5 | 40 | 0.737 | 1994 | 32 | 15.035 | – | 2005 | 24 | 41 | 15.036 | Template:JA-BIN Template:JPL Template:LoMP Template:LCDB | |
15094 Polymele | L4 | 1999 | 21 | citation | CitationClass=web
}}</ref> |
2022 |
Trans-Neptunian objectsEdit
This is a list of trans-Neptunian objects with companions.<ref name="Johnstonsarchive-list" /> Candidate binaries with an unconfirmed status are displayed on a dark background.<ref name="Johnstonsarchive-confirmed-vs-candidates" /> This list gives the companion's orbital period (Ps) in days rather than hours. For an overview, see summary and introduction.
See alsoEdit
- Lists of astronomical objects
- Template:Annotated link
- Template:Annotated link
- Satellite system (astronomy)
ReferencesEdit
External linksEdit
- Template:YouTube, Lecture at SETI talk Template:Small
- Orbits of Binary Asteroids with Adaptive Optics (Franck Marchis)
- Satellites and Companions of Minor Planets (CBAT)
- Asteroids with Satellites Johnston's Archive
- 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)
Template:Asteroids {{#invoke:Navbox|navbox}} Template:Solar System moons (compact) Template:Navbox with columns Template:Portal bar