Asteroid family
Encyclopedia
An asteroid family is a population of asteroid
s that share similar proper orbital elements
, such as semimajor axis, eccentricity, and orbital inclination
. The members of the families are thought to be fragments of past asteroid collisions
.
There are about 20 to 30 reliably recognized families, with several tens of less certain groupings. Most asteroid families are found in the main asteroid belt, although several family-like groups such as the Pallas family
, Hungaria family
, and the Phocaea family
lie at smaller semi-major axis
or larger inclination than the main belt.
One family
has been identified associated with the dwarf planet
. Some studies have tried to find evidence of collisional families among the trojan asteroid
s, but at present the evidence is inconclusive.
, Pallas
, Hygiea
, and Massalia
families). Such cratering families typically consist of a single large body and a swarm of asteroids that are much smaller. Some families (e.g. the Flora family
) have complex internal structures which are not satisfactorily explained at the moment, but may be due to several collisions in the same region at different times.
Due to the method of origin, all the members have closely matching compositions for most families. Notable exceptions are those families (such as the Vesta family
) which formed from a large differentiated
parent body.
Asteroid families are thought to have lifetimes of the order of a billion years, depending on various factors (e.g. smaller asteroids are lost faster). This is significantly shorter than the Solar System's age, so few if any are relics of the early Solar System. Decay of families occurs both because of slow dissipation of the orbits due to perturbations from Jupiter or other large bodies, and because of collisions between asteroids which grind them down to small bodies. Such small asteroids then become subject to perturbations such as the Yarkovsky effect
that can push them towards orbital resonance
s with Jupiter over time. Once there, they are relatively rapidly ejected from the asteroid belt. Tentative age estimates have been obtained for some families, ranging from hundreds of millions of years to less than several million years for e.g. the compact Karin family
. Old families are thought to contain few small members, and this is the basis of the age determinations.
It is supposed that many very old families have lost all the smaller and medium-sized members, leaving only a few of the largest intact. A suggested example of such old family remains are the 9 Metis
and 113 Amalthea
pair. Further evidence for a large number of past families (now dispersed) comes from analysis of chemical ratios in iron meteorite
s. These show that there must have once been at least 50 to 100 parent bodies large enough to be differentiated, that have since been shattered to expose their cores and produce the actual meteorites (Kelley & Gaffey 2000).
vs. eccentricity, or vs. semi-major axis
), a number of distinct concentrations are seen against the rather uniform background distribution of generic asteroids. These concentrations are the asteroid families.
Strictly speaking, families and their membership are identified by analysing the so-called proper orbital elements
rather than the current osculating
orbital elements
, which regularly fluctuate on timescales of tens of thousands of years. The proper elements are related constants of motion that remain almost constant for times of at least tens of millions of years, and perhaps longer.
The Japan
ese astronomer
Kiyotsugu Hirayama
(1874–1943) pioneered the estimation of proper elements for asteroids, and first identified several of the most prominent families in 1918.
In his honor, asteroid families are sometimes called Hirayama families
. This particularly applies to the five prominent groupings discovered by him.
Present day computer-assisted searches have identified several tens of asteroid families. The most prominent algorithms have been the
Hierarchical Clustering Method (HCM) which looks for groupings with small nearest-neighbour distances in orbital element space, and the Wavelet Analysis Method (WAM) which builds a density-of-asteroids map in orbital element space, and looks for density peaks.
The boundaries of the families are somewhat vague because at the edges they blend into the background density of asteroids in the main belt.
For this reason the number of members even among discovered asteroids is usually only known approximately, and membership is uncertain for asteroids near the edges.
Additionally, some interlopers from the heterogeneous background asteroid population are expected even in the central regions of a family.
Since the true family members caused by the collision are expected to have similar compositions, most such interlopers can in principle be recognised by spectral properties which do not match those of the bulk of family members. A prominent example is 1 Ceres
, the largest asteroid, which is an interloper in the family once named after it (the Ceres family, now the Gefion family
).
Spectral characteristics can also be used to determine the membership (or otherwise) of asteroids in the outer regions of a family, as has been used e.g. for the Vesta family
, whose members have an unusual composition.
. Clumps are groupings which have relatively few members but are clearly distinct from the background (e.g. the Juno clump
). Clans are groupings which merge very gradually into the background density and/or have a complex internal structure making it difficult to decide whether they are one complex group or several unrelated overlapping groups (e.g. the Flora family
has been called a clan). Tribes are groups that are less certain to be statistically significant against the background either because of small density or large uncertainty in the orbital parameters of the members.
|-
! rowspan="2" | Family Name
!! rowspan="2" width="110px"| Named After
! colspan="3" align="center" | orbital elements
! colspan="2" aligh="center" | Size
!! rowspan="2" | Alternate Names
|-
! width="80px" |a
(AU
)
!! width="80px" | e
!! width="80px" | i
(°)
!! width="100px" | approx. % of asteroids
!! width="100px" | members in Zappalà
HCM analysis[A]
|-
! colspan="8" | The most prominent families within the main belt are:
|-
|Eos
|| 221 Eos
|| 2.99 to 3.03 || 0.01 to 0.13 || 8 to 12 || || 480 ||
|-
|Eunomia
|| 15 Eunomia
|| 2.53 to 2.72 || 0.08 to 0.22 || 11.1 to 15.8 || 5% || 370 ||
|-
|Flora
|| 8 Flora
|| 2.15 to 2.35 || 0.03 to 0.23 || 1.5 to 8.0 || 4-5%|| 590 || Ariadne family after 43 Ariadne
|-
|Hygiea
|| 10 Hygiea
|| 3.06 to 3.24 || 0.09 to 0.19 || 3.5 to 6.8 || 1% || 105 ||
|-
|Koronis
|| 158 Koronis
|| 2.83 to 2.91 || 0 to 0.11 || 0 to 3.5 || || 310 ||
|-
|Maria || 170 Maria
|| 2.5 to 2.706 || || 12 to 17 || || 80 ||
|-
|Nysa
|| 44 Nysa
|| 2.41 to 2.5 || 0.12 to 0.21 || 1.5 to 4.3 || || 380 || Hertha family after 135 Hertha
|-
|Themis
|| 24 Themis
|| 3.08 to 3.24 || 0.09 to 0.22 || 0 to 3 || || 530 ||
|-
|Vesta
|| 4 Vesta
||2.26 to 2.48||0.03 to 0.16||5.0 to 8.3|| 6% || 240 ||
|-
! colspan="8" | Other notable main belt families:[C]
|-
|Adeona
|| 145 Adeona
|| || || || || 65 ||
|-
|Astrid || 1128 Astrid
|| || || || || 11 ||
|-
|Bower || 1639 Bower
|| || || || || 13 || Endymion family after 342 Endymion
|-
|Brasilia || 293 Brasilia
|| || || || || 14 ||
|-
|Gefion
|| 1272 Gefion
||2.74 to 2.82||0.08 to 0.18||7.4 to 10.5|| 0.8% || 89 || Ceres family after 1 Ceres and
Minerva family after 93 Minerva
|-
|Chloris || 410 Chloris
|| || || || || 24 ||
|-
|Dora || 668 Dora
|| || || || || 78 ||
|-
|Erigone || 163 Erigone
|| || || || || 47 ||
|-
|Hansa || 480 Hansa || ~2.66 || ~0.06 || ~22.0° || || ||
|-
|Hilda
|| 153 Hilda
|| 3.7 to 4.2 || >0.07 || <20° || - || ||
|-
|Karin
|| 832 Karin
|| || || || || 39[B] ||
|-
|Lydia || 110 Lydia
|| || || || || 38 ||
|-
|Massalia
|| 20 Massalia
||2.37 to 2.45||0.12 to 0.21||0.4 to 2.4|| 0.8% || 47 ||
|-
|Meliboea || 137 Meliboea
|| || || || || 15 ||
|-
|Merxia || 808 Merxia
|| || || || || 28 ||
|-
|Misa || 569 Misa
|| || || || || 26 ||
|-
|Naëma || 845 Naëma
|| || || || || 7 ||
|-
|Nemesis || 128 Nemesis
|| || || || || 29 || Concordia family after 58 Concordia
|-
|Rafita || 1644 Rafita
|| || || || || 22 ||
|-
|Veritas || 490 Veritas
|| || || || || 29 || Undina family after 92 Undina
|-
|Theobalda || 778 Theobalda
||3.16 to 3.19 ||0.24 to 0.27 ||14 to 15 || || ||
|-
! colspan="8" | TNO
families:[D]
|-
|Haumea
|| 136108 Haumea || ~43 || ~0.19 || ~28 || || ||
|}
Notes for table:
See also :Category:Asteroid groups and families, which names some less prominent and uncertain groupings.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
s that share similar proper orbital elements
Proper orbital elements
The proper orbital elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale...
, such as semimajor axis, eccentricity, and orbital inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
. The members of the families are thought to be fragments of past asteroid collisions
Collisional family
In astronomy, a collisional family is a group of objects that are thought to have a common origin in an impact . They have similar compositions, and most share similar orbital elements....
.
General properties
Large prominent families contain several hundred recognized asteroids (and many more smaller objects which may be either not-yet-analyzed, or not-yet-discovered). Small, compact families can have only about ten identified members. About 33% to 35% of asteroids in the main belt are family members.There are about 20 to 30 reliably recognized families, with several tens of less certain groupings. Most asteroid families are found in the main asteroid belt, although several family-like groups such as the Pallas family
Pallas family
The Pallas or Palladian family of asteroids is a grouping of B-type asteroids at very high inclinations in the intermediate asteroid belt . It was first noted by Kiyotsugu Hirayama in 1928....
, Hungaria family
Hungaria family
The Hungaria asteroids are a group of asteroids in the asteroid belt that orbit the Sun between 1.78 and 2.00 AU. The asteroids typically have a low eccentricity and an inclination of 16 to 34 degrees....
, and the Phocaea family
Phocaea family
The Phocaea asteroids are a group of asteroids that orbit the Sun between 2.25 and 2.5 AU. Asteroids in this group have orbits with eccentricities greater than 0.1 and inclinations between 18 and 32. The group derives its name from its most massive member, 25 Phocaea.-Asteroids in this Family:...
lie at smaller semi-major axis
Semi-major axis
The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...
or larger inclination than the main belt.
One family
Haumea family
The Haumea family is the only identified trans-Neptunian collisional family; that is, the only group of trans-Neptunian objects with similar orbital parameters and spectra that suggest they originated in the disruptive impact of a progenitor body...
has been identified associated with the dwarf planet
Dwarf planet
A dwarf planet, as defined by the International Astronomical Union , is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite...
. Some studies have tried to find evidence of collisional families among the trojan asteroid
Trojan asteroid
The Jupiter Trojans, commonly called Trojans or Trojan asteroids, are a large group of objects that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of the planet's two Lagrangian points of stability, and , that respectively lie 60° ahead...
s, but at present the evidence is inconclusive.
Origin and evolution
The families are thought to form as a result of collisions between asteroids. In many or most cases the parent body was shattered, but there are also several families which resulted from a large cratering event which did not disrupt the parent body (e.g. the VestaVesta family
The Vesta or Vestian family of asteroids is a large and prominent grouping of mostly V-type asteroids in the inner asteroid belt in the vicinity of 4 Vesta...
, Pallas
Pallas family
The Pallas or Palladian family of asteroids is a grouping of B-type asteroids at very high inclinations in the intermediate asteroid belt . It was first noted by Kiyotsugu Hirayama in 1928....
, Hygiea
Hygiea family
The Hygiea family of asteroids is a grouping of dark, carbonaceous C-type and B-type asteroids in outer main belt, the largest member of which is 10 Hygiea. About 1% of all known main belt asteroids belong to this family.-Characteristics:...
, and Massalia
Massalia family
The Massalia family of asteroids is a grouping of S-type asteroids in the inner main belt at very low inclination. About 0.8% of known asteroids belong to this family.-Characteristics:...
families). Such cratering families typically consist of a single large body and a swarm of asteroids that are much smaller. Some families (e.g. the Flora family
Flora family
The Flora family of asteroids is a large grouping of S-type asteroids in the inner main belt, whose origin and properties are relatively poorly understood at present...
) have complex internal structures which are not satisfactorily explained at the moment, but may be due to several collisions in the same region at different times.
Due to the method of origin, all the members have closely matching compositions for most families. Notable exceptions are those families (such as the Vesta family
Vesta family
The Vesta or Vestian family of asteroids is a large and prominent grouping of mostly V-type asteroids in the inner asteroid belt in the vicinity of 4 Vesta...
) which formed from a large differentiated
Planetary differentiation
In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behaviour, where the body develops into compositionally distinct layers; the denser materials of a planet sink to the center,...
parent body.
Asteroid families are thought to have lifetimes of the order of a billion years, depending on various factors (e.g. smaller asteroids are lost faster). This is significantly shorter than the Solar System's age, so few if any are relics of the early Solar System. Decay of families occurs both because of slow dissipation of the orbits due to perturbations from Jupiter or other large bodies, and because of collisions between asteroids which grind them down to small bodies. Such small asteroids then become subject to perturbations such as the Yarkovsky effect
Yarkovsky effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...
that can push them towards orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
s with Jupiter over time. Once there, they are relatively rapidly ejected from the asteroid belt. Tentative age estimates have been obtained for some families, ranging from hundreds of millions of years to less than several million years for e.g. the compact Karin family
Karin family
The Karin asteroid family or Karin cluster is a sub-family of the Koronis family. It consists of at least 90 main-belt asteroids. What makes them special is that scientists have used the orbits of 13 members to calculate backwards until they were all found to share the same orbit — that of the...
. Old families are thought to contain few small members, and this is the basis of the age determinations.
It is supposed that many very old families have lost all the smaller and medium-sized members, leaving only a few of the largest intact. A suggested example of such old family remains are the 9 Metis
9 Metis
9 Metis is one of the larger main-belt asteroids. It is composed of silicates and metallic nickel-iron, and may be the core remnant of a large asteroid that was destroyed by an ancient collision...
and 113 Amalthea
113 Amalthea
113 Amalthea is a fairly typical rocky main-belt asteroid orbiting in the inner regions of the belt. It was discovered by R. Luther on March 12, 1871....
pair. Further evidence for a large number of past families (now dispersed) comes from analysis of chemical ratios in iron meteorite
Iron meteorite
Iron meteorites are meteorites that consist overwhelmingly of nickel-iron alloys. The metal taken from these meteorites is known as meteoric iron and was one of the earliest sources of usable iron available to humans.-Occurrence:...
s. These show that there must have once been at least 50 to 100 parent bodies large enough to be differentiated, that have since been shattered to expose their cores and produce the actual meteorites (Kelley & Gaffey 2000).
Identification of members and interlopers
When the orbital elements of main belt asteroids are plotted (typically inclinationInclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
vs. eccentricity, or vs. semi-major axis
Semi-major axis
The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...
), a number of distinct concentrations are seen against the rather uniform background distribution of generic asteroids. These concentrations are the asteroid families.
Proper orbital elements
The proper orbital elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale...
rather than the current osculating
Osculating orbit
In astronomy, and in particular in astrodynamics, the osculating orbit of an object in space is the gravitational Kepler orbit In astronomy, and in particular in astrodynamics, the osculating orbit of an object in space (at a given moment of time) is the gravitational Kepler orbit In astronomy,...
orbital elements
Orbital elements
Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are generally considered in classical two-body systems, where a Kepler orbit is used...
, which regularly fluctuate on timescales of tens of thousands of years. The proper elements are related constants of motion that remain almost constant for times of at least tens of millions of years, and perhaps longer.
The Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
Kiyotsugu Hirayama
Kiyotsugu Hirayama
was a Japanese astronomer, best known for his discovery that many asteroid orbits were more similar to one another than chance would allow, leading to the concept of asteroid families, now called "Hirayama families" in his honour....
(1874–1943) pioneered the estimation of proper elements for asteroids, and first identified several of the most prominent families in 1918.
In his honor, asteroid families are sometimes called Hirayama families
Hirayama families
A Hirayama family of asteroids is a group of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination...
. This particularly applies to the five prominent groupings discovered by him.
Present day computer-assisted searches have identified several tens of asteroid families. The most prominent algorithms have been the
Hierarchical Clustering Method (HCM) which looks for groupings with small nearest-neighbour distances in orbital element space, and the Wavelet Analysis Method (WAM) which builds a density-of-asteroids map in orbital element space, and looks for density peaks.
The boundaries of the families are somewhat vague because at the edges they blend into the background density of asteroids in the main belt.
For this reason the number of members even among discovered asteroids is usually only known approximately, and membership is uncertain for asteroids near the edges.
Additionally, some interlopers from the heterogeneous background asteroid population are expected even in the central regions of a family.
Since the true family members caused by the collision are expected to have similar compositions, most such interlopers can in principle be recognised by spectral properties which do not match those of the bulk of family members. A prominent example is 1 Ceres
1 Ceres
Ceres, formally 1 Ceres, is the smallest identified dwarf planet in the Solar System and the only one in the asteroid belt. With a diameter of about 950 km, Ceres is by far the largest and most-massive asteroid, comprising about a third of the mass of the asteroid belt. Discovered on 1 January 1801...
, the largest asteroid, which is an interloper in the family once named after it (the Ceres family, now the Gefion family
Gefion family
The Gefion family of asteroids is a grouping of S-type asteroids in the intermediate main belt.-Properties:The members have proper orbital elements in the approximate ranges...
).
Spectral characteristics can also be used to determine the membership (or otherwise) of asteroids in the outer regions of a family, as has been used e.g. for the Vesta family
Vesta family
The Vesta or Vestian family of asteroids is a large and prominent grouping of mostly V-type asteroids in the inner asteroid belt in the vicinity of 4 Vesta...
, whose members have an unusual composition.
Family types
As previously mentioned, families caused by an impact that did not disrupt the parent body but only ejected fragments are called cratering families. Other terminology has been used to distinguish various types of groups which are less distinct or less statistically certain from the most prominent "nominal families" (or clusters). The term cluster is also used to describe a small asteroid family, such as the Karin ClusterKarin Cluster
The Karin asteroid family or Karin cluster is a sub-family of the Koronis family. It consists of at least 90 main-belt asteroids. What makes them special is that scientists have used the orbits of 13 members to calculate backwards until they were all found to share the same orbit — that of the...
. Clumps are groupings which have relatively few members but are clearly distinct from the background (e.g. the Juno clump
Juno clump
The Juno clump is a probable asteroid family in the vicinity of 3 Juno.3 Juno is a large asteroid with a mean diameter of about 235 km, but the remaining bodies are all small. , the brightest of those clearly in the visible clump would have a diameter of about 6 km, given the same albedo as 3 Juno...
). Clans are groupings which merge very gradually into the background density and/or have a complex internal structure making it difficult to decide whether they are one complex group or several unrelated overlapping groups (e.g. the Flora family
Flora family
The Flora family of asteroids is a large grouping of S-type asteroids in the inner main belt, whose origin and properties are relatively poorly understood at present...
has been called a clan). Tribes are groups that are less certain to be statistically significant against the background either because of small density or large uncertainty in the orbital parameters of the members.
List of families
-
- {| align="center" class="wikitable"
|-
! rowspan="2" | Family Name
!! rowspan="2" width="110px"| Named After
! colspan="3" align="center" | orbital elements
Orbital elements
Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are generally considered in classical two-body systems, where a Kepler orbit is used...
! colspan="2" aligh="center" | Size
!! rowspan="2" | Alternate Names
|-
! width="80px" |a
Semi-major axis
The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...
(AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
)
!! width="80px" | e
!! width="80px" | i
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
(°)
!! width="100px" | approx. % of asteroids
!! width="100px" | members in Zappalà
HCM analysis[A]
|-
! colspan="8" | The most prominent families within the main belt are:
|-
|Eos
Eos family
The Eos or Eoan family is a prominent family of main belt asteroids that is believed to have formed as a result of an ancient catastrophic collision. Members of the family share similar orbits. The family is named after 221 Eos....
|| 221 Eos
221 Eos
221 Eos is a rather large main-belt asteroid. It is classified as a K-type asteroid. It is a member of the extensive Eos asteroid family, which is named after it.Eos was discovered by Johann Palisa on January 18, 1882, in Vienna...
|| 2.99 to 3.03 || 0.01 to 0.13 || 8 to 12 || || 480 ||
|-
|Eunomia
Eunomia family
The Eunomia family of asteroids is a large grouping of S-type asteroids named after the Greek goddess Eunomia. It is the most prominent family in the intermediate main belt...
|| 15 Eunomia
15 Eunomia
15 Eunomia is a very large asteroid in the inner asteroid belt. It is the largest of the stony asteroids, and somewhere between the 8th-to-12th-largest main-belt asteroid overall...
|| 2.53 to 2.72 || 0.08 to 0.22 || 11.1 to 15.8 || 5% || 370 ||
|-
|Flora
Flora family
The Flora family of asteroids is a large grouping of S-type asteroids in the inner main belt, whose origin and properties are relatively poorly understood at present...
|| 8 Flora
8 Flora
8 Flora is a large, bright main-belt asteroid. It is the innermost large asteroid: no asteroid closer to the Sun has a diameter above 25 kilometres or two-elevenths that of Flora itself, and not until the tiny 149 Medusa was discovered was a single asteroid orbiting at a closer mean distance...
|| 2.15 to 2.35 || 0.03 to 0.23 || 1.5 to 8.0 || 4-5%|| 590 || Ariadne family after 43 Ariadne
43 Ariadne
43 Ariadne is a fairly large and bright main-belt asteroid. It is the second-largest member of the Flora asteroid family. It was discovered by N. R. Pogson on April 15, 1857, and named after the Greek heroine Ariadne.-Characteristics:...
|-
|Hygiea
Hygiea family
The Hygiea family of asteroids is a grouping of dark, carbonaceous C-type and B-type asteroids in outer main belt, the largest member of which is 10 Hygiea. About 1% of all known main belt asteroids belong to this family.-Characteristics:...
|| 10 Hygiea
10 Hygiea
10 Hygiea is an asteroid located in the asteroid belt. With somewhat oblong diameters of 350–500 km, and a mass estimated to be 2.9% of the total mass of the belt, it is the fourth largest asteroid by volume and mass...
|| 3.06 to 3.24 || 0.09 to 0.19 || 3.5 to 6.8 || 1% || 105 ||
|-
|Koronis
Koronis family
]The Koronis family is a family of asteroids in the main belt between Mars and Jupiter. They are thought to have been formed at least two billion years ago in a catastrophic collision between two larger bodies. The largest known is about in diameter. The Koronis family travels in a cluster along...
|| 158 Koronis
158 Koronis
158 Koronis is a main-belt, S-type asteroid.It was discovered by Viktor Knorre on January 4, 1876, from the Berlin observatory. It was the first of his four asteroid discoveries....
|| 2.83 to 2.91 || 0 to 0.11 || 0 to 3.5 || || 310 ||
|-
|Maria || 170 Maria
170 Maria
170 Maria is a Main belt asteroid. It is an S-type asteroid.It is the namesake of the Maria asteroid family.It was discovered by J. Perrotin on January 10, 1877. Its orbit was computed by Antonio Abetti, and the asteroid was named after his sister, Maria....
|| 2.5 to 2.706 || || 12 to 17 || || 80 ||
|-
|Nysa
Nysa family
The Nysa or Nysian asteroids are a group of asteroids in the Main Belt orbiting the sun between 2.41 and 2.5 AU. Asteroids in this family have eccentricities between 0.12 and 0.21 and inclinations of 1.4 to 4.3...
|| 44 Nysa
44 Nysa
44 Nysa is a large and very bright main-belt asteroid, and the brightest member of the Nysian asteroid family. It is classified as a rare class E asteroid and is probably the largest of this type .-Discovery:...
|| 2.41 to 2.5 || 0.12 to 0.21 || 1.5 to 4.3 || || 380 || Hertha family after 135 Hertha
135 Hertha
135 Hertha is a large main-belt asteroid. Named Hertha, another name for Nerthus, a Germanic fertility goddess. It orbits among the Nysa asteroid family but its classification as an M-type asteroid does not match the more common F-type asteroid for this family, suggesting that it may be an interloper...
|-
|Themis
Themis family
The Themis or Themistian Asteroid Family is a Hirayama family of asteroids found in the outer portion of the main asteroid belt, between the orbits of Mars and Jupiter. At a mean distance of 3.13 AU from the Sun, it is one of the more populous asteroid families...
|| 24 Themis
24 Themis
24 Themis is one of the largest main-belt asteroids. It is also the largest member of the Themistian asteroid family. It was discovered by Annibale de Gasparis on April 5, 1853...
|| 3.08 to 3.24 || 0.09 to 0.22 || 0 to 3 || || 530 ||
|-
|Vesta
Vesta family
The Vesta or Vestian family of asteroids is a large and prominent grouping of mostly V-type asteroids in the inner asteroid belt in the vicinity of 4 Vesta...
|| 4 Vesta
4 Vesta
Vesta, formally designated 4 Vesta, is one of the largest asteroids, with a mean diameter of about . It was discovered by Heinrich Wilhelm Olbers on March 29, 1807, and is named after the Roman virgin goddess of home and hearth, Vesta....
||2.26 to 2.48||0.03 to 0.16||5.0 to 8.3|| 6% || 240 ||
|-
! colspan="8" | Other notable main belt families:[C]
|-
|Adeona
Adeona family
The Adeona family is an asteroid family that formed from the parent body 145 Adeona. There are an estimated 1,000 Adeonian asteroids....
|| 145 Adeona
145 Adeona
145 Adeona is a rather large main-belt asteroid. Its surface is very dark, and probably composed of primitive carbonaceous material. The Adeona family of asteroids is named after it....
|| || || || || 65 ||
|-
|Astrid || 1128 Astrid
1128 Astrid
1128 Astrid is a main belt asteroid orbiting the Sun. Approximately 35 kilometers in diameter, it makes a revolution around the Sun once every 5 years. It was discovered by Eugène Joseph Delporte at Uccle, Belgium on March 10, 1929. It was named for H.M. Astrid, Queen of the Belgians. Its...
|| || || || || 11 ||
|-
|Bower || 1639 Bower
1639 Bower
1639 Bower is a main-belt asteroid discovered on September 12, 1951 by Sylvain Julien Victor Arend at Uccle.- External links :*...
|| || || || || 13 || Endymion family after 342 Endymion
342 Endymion
342 Endymion is a large Main belt asteroid.It was discovered by Max Wolf on October 17, 1892 in Heidelberg....
|-
|Brasilia || 293 Brasilia
293 Brasilia
293 Brasilia is a large Main belt asteroid.It was discovered by Auguste Charlois on May 20, 1890 in Nice....
|| || || || || 14 ||
|-
|Gefion
Gefion family
The Gefion family of asteroids is a grouping of S-type asteroids in the intermediate main belt.-Properties:The members have proper orbital elements in the approximate ranges...
|| 1272 Gefion
1272 Gefion
1272 Gefion is an asteroid from the asteroid belt discovered on October 10, 1931 by Reinmuth, K. at Heidelberg.-References:...
||2.74 to 2.82||0.08 to 0.18||7.4 to 10.5|| 0.8% || 89 || Ceres family after 1 Ceres and
Minerva family after 93 Minerva
93 Minerva
93 Minerva is a large trinary main-belt asteroid. It is a C-type asteroid, meaning that it has a dark surface and possibly a primitive carbonaceous composition. It was discovered by J. C. Watson on August 24, 1867, and named after Minerva, the Roman equivalent of Athena, goddess of wisdom...
|-
|Chloris || 410 Chloris
410 Chloris
410 Chloris is a very large main-belt asteroid. It is classified as a C-type asteroid and is probably composed of primitive carbonaceous material. It is the namesake of the Chloris family of asteroids....
|| || || || || 24 ||
|-
|Dora || 668 Dora
668 Dora
- External links :*...
|| || || || || 78 ||
|-
|Erigone || 163 Erigone
163 Erigone
163 Erigone is a dark-coloured, fairly big Main belt asteroid, the namesake of the Erigone family of asteroids. It was discovered by J. Perrotin on April 26, 1876 and named after one of the two Erigones in Greek mythology....
|| || || || || 47 ||
|-
|Hansa || 480 Hansa || ~2.66 || ~0.06 || ~22.0° || || ||
|-
|Hilda
Hilda family
The Hilda asteroids consists of asteroids with a semi-major axis between 3.7 AU and 4.2 AU, an eccentricity less than 0.3, and an inclination less than 20°. They do not form a true asteroid family, in the sense that they do not descend from a common parent object. Instead, this is a dynamical...
|| 153 Hilda
153 Hilda
153 Hilda is a large asteroid in the outer main belt, with a diameter of 170 km. Because it is composed of primitive carbonaceous materials, it has a very dark surface. It was discovered by Johann Palisa on November 2, 1875 from the Austrian Naval Observatory at Pula...
|| 3.7 to 4.2 || >0.07 || <20° || - || ||
|-
|Karin
Karin family
The Karin asteroid family or Karin cluster is a sub-family of the Koronis family. It consists of at least 90 main-belt asteroids. What makes them special is that scientists have used the orbits of 13 members to calculate backwards until they were all found to share the same orbit — that of the...
|| 832 Karin
832 Karin
832 Karin is a minor planet orbiting the Sun. It is named after Queen Karin Månsdotter It is the largest member of the Karin Cluster, which is named after it. Found in 2002, the Karin cluster is notable for being very young...
|| || || || || 39[B] ||
|-
|Lydia || 110 Lydia
110 Lydia
110 Lydia is a quite large main-belt asteroid with an M-type spectrum, which may contain nickel-iron. The asteriod has a fairly circular orbit around the sun. The Lydia asteroid family is named after it. It was discovered by A. Borrelly on April 19, 1870...
|| || || || || 38 ||
|-
|Massalia
Massalia family
The Massalia family of asteroids is a grouping of S-type asteroids in the inner main belt at very low inclination. About 0.8% of known asteroids belong to this family.-Characteristics:...
|| 20 Massalia
20 Massalia
20 Massalia is a large and fairly bright main-belt asteroid. It is also the largest member of the Massalia family of asteroids. Its name is the Greek name for Marseille, the city from which one of the two independent co-discovers, Jean Chacornac, first sighted it.- Characteristics :Massalia is an...
||2.37 to 2.45||0.12 to 0.21||0.4 to 2.4|| 0.8% || 47 ||
|-
|Meliboea || 137 Meliboea
137 Meliboea
137 Meliboea is a large and very dark main-belt asteroid. It is composed of carbonaceous materials. It is the largest body in the Meliboea family of asteroids. Only 791 Ani approaches its size. It was discovered by J. Palisa on April 21, 1874, the second of his many asteroid discoveries. It is...
|| || || || || 15 ||
|-
|Merxia || 808 Merxia
808 Merxia
-External links:*...
|| || || || || 28 ||
|-
|Misa || 569 Misa
569 Misa
- External links :*...
|| || || || || 26 ||
|-
|Naëma || 845 Naëma
845 Naëma
-External links:*...
|| || || || || 7 ||
|-
|Nemesis || 128 Nemesis
128 Nemesis
128 Nemesis is a very large and very dark main-belt asteroid, of carbonaceous composition. It rotates rather slowly, taking about one and half Earth days to complete one revolution. Nemesis is the largest member of the Nemesian asteroid family bearing its name. It was discovered by J. C...
|| || || || || 29 || Concordia family after 58 Concordia
58 Concordia
58 Concordia is a fairly large asteroid-belt asteroid. It is classified as a C-type asteroid, meaning that its surface is very dark and it is likely carbonaceous in composition.Concordia was discovered by Robert Luther on March 24, 1860...
|-
|Rafita || 1644 Rafita
1644 Rafita
1644 Rafita is a main-belt asteroid discovered on December 16, 1935 by R. Carrasco at Madrid.- External links :*...
|| || || || || 22 ||
|-
|Veritas || 490 Veritas
490 Veritas
490 Veritas is a large asteroid, which may have been involved in one of the more massive asteroid-asteroid collisions of the past 100 million years....
|| || || || || 29 || Undina family after 92 Undina
92 Undina
92 Undina is a large main belt asteroid. It has an unusually high albedo and an M-type spectrum. It was discovered by C. H. F. Peters on July 7, 1867. It is named for the eponymous heroine of Undine, a popular novella by Friedrich de la Motte Fouqué. Undina is a member of the Veritas asteroid...
|-
|Theobalda || 778 Theobalda
778 Theobalda
778 Theobalda is a minor planet orbiting the Sun, in the main asteroid belt. It was discovered by Franz Kaiser on 25 January 1914.- External links :*...
||3.16 to 3.19 ||0.24 to 0.27 ||14 to 15 || || ||
|-
! colspan="8" | TNO
Trans-Neptunian object
A trans-Neptunian object is any minor planet in the Solar System that orbits the Sun at a greater distance on average than Neptune.The first trans-Neptunian object to be discovered was Pluto in 1930...
families:[D]
|-
|Haumea
Haumea family
The Haumea family is the only identified trans-Neptunian collisional family; that is, the only group of trans-Neptunian objects with similar orbital parameters and spectra that suggest they originated in the disruptive impact of a progenitor body...
|| 136108 Haumea || ~43 || ~0.19 || ~28 || || ||
|}
Notes for table:
- [A]: Mean of the "core" members found in HCM and WAM analyses by Zappala et al. (1995), rounded to 2 significant digits. That analysis considered 12487 asteroids, but currently over 300,000 are known (an increase by a factor of over 25). Hence, the number of currently catalogued asteroids that are members of a given family is likely to be greater than the value in this column by a similar factor of roughly 25.
- [B]: Reference elsewhere.
- [C]: Most of these are families listed as "robustly" identified in Bendjoya and Zappala (2002). Exception: Karin family.
- [D]: TNOs are not considered asteroids, but are included here for completeness.
See also :Category:Asteroid groups and families, which names some less prominent and uncertain groupings.
See also
- asteroidAsteroidAsteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
- minor planetMinor planetAn asteroid group or minor-planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid...
- main belt
- Hirayama familiesHirayama familiesA Hirayama family of asteroids is a group of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination...
- proper orbital elementsProper orbital elementsThe proper orbital elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale...
- :Category:Asteroid groups and families
External links
- Planetary Data System - Asteroid Families dataset, as per the Zappalà 1995 analysis.
- Latest calculations of proper elements for numbered minor planets at astDys.
- Asteroid (and Comet) Groups by Petr Scheirich (with excellent plots).