The Hygiea or Hygieanfamily is a grouping of dark, carbonaceous C-type and B-type asteroids in outer asteroid belt, the largest member of which is 10 Hygiea. About 1% of all known asteroids in the asteroid belt belong to this family.
By far the largest member is 10 Hygiea, a 400 km diameter C-type asteroid that is the fourth largest in the belt. The remaining members are much smaller so Hygiea contains about 94–98% of the mass in the family (depending on the exact criteria for inclusion). The two next largest members are 333 Badenia, and 538 Friederike, both just over 70 km in diameter. After that, the remaining members have diameters of less than 30 km.
The Hygiea family is thought to have arisen from a catastrophically disruptive impact, after which Hygiea re-accumulated. The two 70-kilometer-diameter bodies, which are much larger than, for example, the Vesta family, which contains no members above around 10 km in diameter, are consistent with this scenario.
The family contains a significant number of objects of the otherwise rare B spectral type (Mothé-Diniz 2001). The largest of these is the previously mentioned 538 Friederike.
There are some indications that this family is relatively quite old (Tanga 1999).
A HCM numerical analysis by (Zappala 1995) found a 'core' group of family members, whose proper orbital elements lie in the approximate ranges
ap | ep | ip | |
---|---|---|---|
min | 3.06 AU | 0.109 | 4.2° |
max | 3.22 AU | 0.163 | 5.8° |
At the present epoch, the range of osculating orbital elements of these core members is
a | e | i | |
---|---|---|---|
min | 3.06 AU | 0.088 | 3.5° |
max | 3.24 AU | 0.191 | 6.8° |
The 1995 analysis by Zappalà found 103 core members, whereas a search of a recent proper element database (AstDys)for 96944 minor planets in 2005 yielded 1043 objects lying within the rectangular-shaped region defined by the first table above. This would give about 1% of all asteroids in the asteroid belt.
This family contains quite a large number of identified interlopers. The following have been identified in a spectral survey (Mothé-Diniz 2001), and also by inspection of the PDS asteroid taxonomy data set for S- and D-type members: 100 Hekate, 108 Hecuba, 1109 Tata, 1209 Pumma, and 1599 Giomus.
In fact, some of the other asteroids of the C spectral type are probably interlopers as well, due to the prevalence of this spectral type in the region. Possible candidates include 333 Badenia and 538 Friederike, based on their unusually large size for cratering family members.
52 Europa, a very large 300 km diameter asteroid, orbits nearby with a proper inclination of 6.37°, and was sometimes considered part of the Hygiea family in the past, but it is an unrelated asteroid. A better sampling of asteroids in the area in recent years has clearly shown that it orbits well beyond the Hygiea family clump.
10 Hygiea is a major asteroid located in the main asteroid belt. With a mean diameter of between 425 and 440 km and a mass estimated to be 3% of the total mass of the belt, it is the fourth-largest asteroid in the Solar System by both volume and mass, and is the largest of the C-type asteroids in classifications that use G type for 1 Ceres. It is very close to spherical, apparently because it had re-accreted after the disruptive impact that produced the large Hygiean family of asteroids.
31 Euphrosyne is a very young asteroid. It is one of the largest asteroids. It was discovered by James Ferguson on September 1, 1854, the first asteroid found from North America. It is named after Euphrosyne, one of the Charites in Greek mythology. In 2019 a small companion was discovered. It is the third-roundest known asteroid ; this is thought to be due to having re-accreted after being disrupted by a collision, and it is not close to hydrostatic equilibrium.
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 15 April 1857 and named after the Greek heroine Ariadne.
The Eunomia or Eunomian family is a large asteroid family of S-type asteroids named after the asteroid 15 Eunomia. It is the most prominent family in the intermediate asteroid belt and the 6th-largest family with nearly six thousand known members, or approximately 1.4% of all asteroids in the asteroid belt.
100 Hekate is a large main-belt asteroid.
An asteroid family is a population of asteroids 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. An asteroid family is a more specific term than asteroid group whose members, while sharing some broad orbital characteristics, may be otherwise unrelated to each other.
255 Oppavia is a sizeable Main belt asteroid. It was discovered by Austrian astronomer Johann Palisa on 31 March 1886 in Vienna and was named after Opava, a town in the Czech Republic, then part of Austria-Hungary, where Palisa was born. It is orbiting the Sun at a distance of 2.75 AU with an orbital eccentricity (ovalness) of 0.077 and a period of 4.55 yr. The orbital plane is inclined by an angle of 9.47° to the plane of the ecliptic.
The Vesta family is a family of asteroids. The cratering family is located in the inner asteroid belt in the vicinity of its namesake and principal body, 4 Vesta. It is one of the largest asteroid families with more than 15,000 known members and consists of mostly bright V-type asteroids, so-called "vestoids".
The Gefion family is an asteroid family located in the intermediate asteroid belt between 2.74 and 2.82 AU at inclinations of 7.4° to 10.5°. The family of S-type asteroids is named after 1272 Gefion and consists of more than 2,500 known members. It had previously been known as the Ceres family. It is still known as Minerva family, named after then thought parent body 93 Minerva, until it was identified to be an interloper into its own family.
538 Friederike is a minor planet orbiting in the asteroid belt. It is a member of the Hygiea family of asteroids.
763 Cupido is a Flora asteroid, tumbler and slow rotator from the inner regions of the asteroid belt, approximately 7 kilometers in diameter. It was discovered on 25 September 1913, by German astronomer Franz Kaiser at the Heidelberg-Königstuhl State Observatory in southwest Germany. The S/L-type asteroid has an exceptionally long rotation period of 151 hours. It was named by its Latin name after Cupid, the Roman god of erotic love, attraction and affection.
779 Nina is a large background asteroid, approximately 80 kilometers in diameter, located in the central region of the asteroid belt. It was discovered on 25 January 1914, by Russian astronomer Grigory Neujmin(1886-1946) at the Simeiz Observatory on the Crimean peninsula. The metallic X-type asteroid with an intermediate albedo has a rotation period of 11.2 hours. It was named after the discoverer's sister, Nina Neujmina (Tsentilovich) (1889–1971).
817 Annika is a background asteroid in the region of the Eunomia family, located in the central portion of the asteroid belt. It was discovered on 6 February 1916, by German astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany. The stony S-type asteroid (Sl) has a rotation period of 10.56 hours and measures approximately 23 kilometers in diameter. Any reference of the asteroid's name to a person is unknown.
848 Inna is a carbonaceous Themistian asteroid from the outer regions of the asteroid belt. It was discovered on 5 September 1915, by astronomer Grigory Neujmin at the Simeiz Observatory on the Crimean peninsula. The C-type asteroid measures approximately 33 kilometers in diameter, while its rotation period remains unknown. It was named after Russian astronomer Inna Nikolaevna Leman-Balanovskaya (1881–1945).
867 Kovacia is an elongated, dark asteroid and member of the Hygiea family from the outer regions of the asteroid belt. It was discovered on 25 February 1917, by astronomer Johann Palisa at the Vienna Observatory in Austria. The carbonaceous C/B-type asteroid has a rotation period of 8.7 hours and measures approximately 24 kilometers in diameter. It was named after Austrian physician Friedrich Kovacs (1861–1931).
929 Algunde, is a stony Flora asteroid from the inner regions of the asteroid belt, that measures approximately 11 kilometers in diameter. It was discovered by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory on 10 March 1920. The S-type asteroid has a short rotation period of 3.3 hours and is likely spherical in shape. It was named "Algunde", a common German female name unrelated to the discoverer's contemporaries, that was taken from the almanac Lahrer Hinkender Bote.
The Flora family is a prominent family of stony asteroids located in the inner region of the asteroid belt. It is one of the largest families with more than 13,000 known members, or approximately 3.5% of all main-belt asteroids.
The Massalia family is a family of asteroids in the inner asteroid belt, named after its parent body, 20 Massalia. It consists of S-type asteroids with very low inclinations, straddling the 1:2 resonances with Mars. There are more than 6,000 known Massalian asteroids.
1419 Danzig is a highly elongated Flora asteroid from the inner regions of the asteroid belt. It was discovered on 5 September 1929, by German astronomer Karl Reinmuth at Heidelberg Observatory in southwest Germany. The stony S-type asteroid has a rotation period of 8.1 hours and measures approximately 14 kilometers in diameter. It was named for the city of Gdańsk.
6312 Robheinlein (prov. designation:1990 RH4) is a bright Augusta or background asteroid from the inner regions of the asteroid belt, that measures approximately 3.5 kilometers (2.2 miles) in diameter. It was discovered on 14 September 1990, by American astronomer Henry Holt at the Palomar Observatory in California. The uncommon L-type asteroid was named for American science fiction writer Robert A. Heinlein.