Eunomia family

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The Eunomia or Eunomian family ( FIN: 502 ) 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. [1] [2] : 23 

Contents

Characteristics

Location and structure of the Eunomia family. Eunomia family.png
Location and structure of the Eunomia family.

By far the largest member is 15 Eunomia, the largest of all the "stony" S-type asteroid, It is about 300 km across along its longest axis, has a 250 km mean radius, and lies close to the barycenter of the family. Eunomia has been estimated to contain about 70–75% of the matter from the original parent body. This had a mean diameter of about 280 km and was disrupted by the catastrophic impact that created the family. [3] It is likely that the parent body was at least partly differentiated, because the surface of Eunomia and spectra of the smaller family members show some variation. [4] [5] [6] This notwithstanding, other studies have indicated that the body that was definitively shattered by the impact that created the family was probably already somewhat fragmented by previous smaller collisions. [7] The impactor was probably a smaller, yet still very substantial asteroid of 50 km diameter (or so) that hit at a speed of about 22,000 km/h. [8]

The other Eunomian asteroids are quite regularly distributed in orbital space around Eunomia. The next largest member identified by the [9] analysis was 258 Tyche of 65 km diameter. However, its orbit lies at the very margin of what can be considered the family region, and it may well be an interloper. The largest clear family members are about 30 km diameter, with several asteroids in this size range.

Spectroscopic studies have shown that the family members span a noticeable range of compositions, although all remain within the S spectral class. As such they are of generally stony (rather than icy) surface composition that includes silicates and some nickel-iron, and are quite bright for their size.

The family contains relatively large numbers of small objects. Since most of these smaller objects are "eroded" away over time due to secondary collisions, gravitational perturbations, and the Yarkovsky effect, this indicates that the Eunomia family was created relatively recently (on an astronomical timescale). [8] [10]

The Cassini-Huygens spacecraft flew by 2685 Masursky, a small family member, in 2000. However, the encounter distance of about one million kilometers was too large for surface features to be resolved.

Location and size

The Eunomia family is located between the 3:1 and 8:3 resonances with Jupiter, at relatively high inclinations.

A HCM numerical analysis by Zappalà, et al. [9] determined a large group of 'core' family members, whose proper orbital elements lie in the approximate ranges

ap ep ip
min2.54  AU 0.12111.6°
max2.72 AU0.18014.8°

At the present epoch, the range of osculating orbital elements of these core members is

a e i
min2.53  AU 0.07811.1°
max2.72 AU0.21815.8°

The Zappalà 1995 analysis found 439 core members, while a search of a recent proper element database [11] for 96944 minor planets in 2005 yielded 4649 objects lying within the rectangular-shaped region defined by the first table above. By 2014, Nesvorný identified at total of 5,670, or approximately 1.4% of all asteroids, using the Hierarchical Clustering Method. [1] [2] : 23 

Interlopers

A number of interlopers have been identified, which share the same orbital elements as the true family members, but can not have come from the same breakup because of spectral (hence, compositional) differences. The following have been identified in a spectral survey: 85 Io, 141 Lumen, 546 Herodias. [5] [12] : 646 

Related Research Articles

<span class="mw-page-title-main">624 Hektor</span> Largest Jupiter trojan

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.

<span class="mw-page-title-main">2685 Masursky</span> Small Eunomian Asteroid

2685 Masursky, provisional designation 1981 JN, is a stony Eunomian asteroid from the central regions of the asteroid belt, approximately 11 kilometers in diameter. It was discovered on 3 May 1981, by American astronomer Edward Bowell at the Anderson Mesa Station near Flagstaff, Arizona, and named after American planetary geologist Harold Masursky. In January 2000, the Cassini space probe observed the S-type asteroid from afar during its coast to Saturn.

<span class="mw-page-title-main">15 Eunomia</span> Main-belt asteroid

Eunomia is a very large asteroid in the middle asteroid belt. It is the largest of the stony (S-type) asteroids, with 3 Juno as a close second. It is quite a massive asteroid, in 6th to 8th place. It is the largest Eunomian asteroid, and is estimated to contain 1% of the mass of the asteroid belt.

<span class="mw-page-title-main">43 Ariadne</span> Main-belt asteroid

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.

<span class="mw-page-title-main">63 Ausonia</span> Main-belt asteroid

Ausonia is a stony Vestian asteroid from the inner region of the asteroid belt, approximately 100 kilometers in diameter. It was discovered by Italian astronomer Annibale de Gasparis on 10 February 1861, from the Astronomical Observatory of Capodimonte, in Naples, Italy. The initial choice of name for the asteroid was "Italia", after Italy, but this was modified to Ausonia, an ancient classical name for the Italian region.

<span class="mw-page-title-main">Asteroid family</span> Asteroid population sharing similar proper orbital elements

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.

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 Eos family is a very large asteroid family located in the outer region of the asteroid belt. The family of K-type asteroids is believed to have formed as a result of an ancient catastrophic collision. The family's parent body is the asteroid 221 Eos.

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.

<span class="mw-page-title-main">Pallas family</span>

The Pallas family is a small asteroid family of B-type asteroids at very high inclinations in the intermediate asteroid belt.

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).

<span class="mw-page-title-main">867 Kovacia</span>

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).

<span class="mw-page-title-main">812 Adele</span>

812 Adele is an elongated Eunomia asteroid from the central regions of the asteroid belt. It was discovered on 8 September 1915, by Russian astronomer Sergey Belyavsky at the Simeiz Observatory on the Crimean peninsula. The presumed S-type asteroid has a rotation period of 5.9 hours and measures approximately 13 kilometers in diameter. It was likely named after the character "Adele" in the opera Die Fledermaus by Johann Strauss.

845 Naëma is a large asteroid and the parent body of the Naëma family located in the outer regions of the asteroid belt. It was discovered on 16 November 1916, by astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany. The carbonaceous C-type asteroid has a rotation period of 20.9 hours and measures approximately 54 kilometers in diameter on average, as it is likely elongated in shape. Any reference of the asteroid's name to a person is unknown.

<span class="mw-page-title-main">Juno clump</span>

The Juno clump is a probable main-belt asteroid family that share similar orbital elements to 3 Juno.

<span class="mw-page-title-main">Flora family</span> Grouping of S-type asteroids

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 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.

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.

The Nysa family is part of the Nysa–Polana complex, the largest cluster of asteroid families in the asteroid belt. It is located in the inner region of the asteroid belt, orbiting the Sun between 2.41 and 2.5 AU. Asteroids in this complex have eccentricities between 0.12 and 0.21 and inclinations of 1.4 to 4.3. The family derives its name from its most massive member, 44 Nysa. It has also been known as the Hertha family(adj. Herthian) named after 135 Hertha.

References

  1. 1 2 "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Archived from the original on 9 October 2016. Retrieved 27 October 2017.
  2. 1 2 Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families". Asteroids IV. pp. 297–321. arXiv: 1502.01628 . Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN   9780816532131.
  3. ↑ Tanga, P.; Cellino, Alberto; Michel, Patrick; Zappalà, Vincenzo; Paolicchi, P.; Dell'Oro, A. (1999). "On the Size Distribution of Asteroid Families: The Role of Geometry". Icarus. 141 (1): 65. Bibcode:1999Icar..141...65T. doi:10.1006/icar.1999.6148.[ dead link ]
  4. ↑ Reed, K. L.; Gaffey, M. J.; Lebofsky, L. A. (1997). "Shape and Albedo Variations of Asteroid 15 Eunomia". Icarus. 125 (2): 446. Bibcode:1997Icar..125..446R. doi:10.1006/icar.1996.5627.[ dead link ]
  5. 1 2 Lazzaro, D.; Mothé-Diniz, T.; Carvano, J. M.; Angeli, C. A.; Betzler, A. S.; Florczak, M.; Cellino, Alberto; Di Martino, M.; Doressoundiram, A.; Barucci, M. A.; Dotto, E.; Bendjoya, Philippe (1999). "The Eunomia Family: A Visible Spectroscopic Survey". Icarus. 142 (2): 445. Bibcode:1999Icar..142..445L. doi:10.1006/icar.1999.6213.
  6. ↑ Nathues, A.; Mottola, S.; Kaasalainen, M.; Neukum, G. (2005). "Spectral study of the Eunomia asteroid family; I. Eunomia". Icarus. 175 (2): 452. Bibcode:2005Icar..175..452N. doi:10.1016/j.icarus.2004.12.013.[ dead link ]
  7. ↑ Michel, Patrick; Benz, W.; Richardson, D. C. (2004). "Catastrophic disruption of pre-shattered parent bodies". Icarus. 168 (2): 420. Bibcode:2004Icar..168..420M. doi:10.1016/j.icarus.2003.12.011.[ dead link ]
  8. 1 2 Michel, Patrick; Benz, W.; Tanga, P.; Richardson, D. C. (2001). "Collisional and Gravitational Reaccumulation: Forming Asteroid Families and Satellites". Science. 294 (5547): 1696–700. Bibcode:2001Sci...294.1696M. doi:10.1126/science.1065189. PMID   11721050. S2CID   6470148.
  9. 1 2 Zappalà, Vincenzo; Bendjoya, Philippe; Cellino, Alberto; Farinella, Paolo; Froeschlé, Claude (August 1995). "Asteroid Families: Search of a 12,487-Asteroid Sample Using Two Different Clustering Techniques". Icarus. 116 (2): 291–314. Bibcode:1995Icar..116..291Z. doi:10.1006/icar.1995.1127.
  10. ↑ Michel, Patrick; Tanga, P.; Benz, W.; Richardson, D. C. (2002). "Formation of Asteroid Families by Catastrophic Disruption: Simulations with Fragmentation and Gravitational Reaccumulation". Icarus. 160 (1): 10. Bibcode:2002Icar..160...10M. doi:10.1006/icar.2002.6948.[ dead link ]
  11. ↑ "Proper elements for 96944 numbered minor planets". AstDys site. Archived from the original on 2006-02-20. Retrieved 2006-05-09.
  12. ↑ Cellino, A.; Bus, S. J.; Doressoundiram, A.; Lazzaro, D. (March 2002). "Spectroscopic Properties of Asteroid Families" (PDF). Asteroids III: 633–643. Bibcode:2002aste.book..633C . Retrieved 27 October 2017.
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