4138 Kalchas
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| Discovery[1] | |
|---|---|
| Discovered by | C. J. van Houten I. van Houten-G. T. Gehrels |
| Discovery site | Palomar Obs. |
| Discovery date | 19 September 1973 |
| Designations | |
| (4138) Kalchas | |
| Pronunciation | /ˈkælkəs/ |
Named after | Calchas[1] (Greek mythology) |
| 1973 SM · 1986 VU6 | |
| Jupiter trojan[1][2] Greek[3] · background[4] | |
| Adjectives | Kalchantian |
| Orbital characteristics[2] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 61.48 yr (22,454 d) |
| Aphelion | 5.3874 AU |
| Perihelion | 4.9395 AU |
| 5.1634 AU | |
| Eccentricity | 0.0434 |
| 11.73 yr (4,286 d) | |
| 283.43° | |
| 0° 5m 2.4s / day | |
| Inclination | 2.0993° |
| 208.02° | |
| 164.17° | |
| Jupiter MOID | 0.019 AU |
| TJupiter | 2.9970 |
| Physical characteristics | |
| 46.46±0.67 km[5] 61.04±3.49 km[6] | |
| 29.2±0.1 h[7] | |
| 0.057±0.007[6] 0.082±0.006[5] | |
| C (assumed)[8] V–I = 0.810±0.038[8] | |
| 9.80[6] 10.0[5] 10.1[1][2][8] | |
4138 Kalchas /ˈkælkəs/ is a large Jupiter trojan from the Greek camp, approximately 53 kilometers (33 miles) in diameter. It was discovered on 19 September 1973 by Dutch astronomers Ingrid and Cornelis van Houten at Leiden on photographic plates taken by Tom Gehrels at the Palomar Observatory in California.[1] The assumed C-type asteroid is the principal body of the proposed Kalchas family and has a rotation period of 29.2 hours.[8] It was named after the seer Calchas from Greek mythology.[1]
Palomar–Leiden Trojan survey
Kalchas is a dark Jovian asteroid in a 1:1 orbital resonance with Jupiter. It is located in the leading Greek camp at the Gas Giant's L4 Lagrangian point, 60° ahead of its orbit .[3] It orbits the Sun at a distance of 4.9–5.4 AU once every 11 years and 9 months (4,286 days; semi-major axis of 5.16 AU). Its orbit has an eccentricity of 0.04 and an inclination of 2° concerning the ecliptic.[2] The body's observation arc begins with a precovery taken at Palomar in May 1956, more than 17 years before its official discovery observation.[1]
While the discovery date aligns with the second Palomar–Leiden Trojan survey, Kalchas did not receive a "T-2" prefixed survey designation, which was assigned for the discoveries made by the fruitful collaboration between the Palomar and Leiden observatories in the 1960s and 1970s. Gehrels used Palomar's Samuel Oschin telescope (also known as the 48-inch Schmidt Telescope) and shipped the photographic plates to Ingrid and Cornelis van Houten at Leiden Observatory, where astrometry was carried out. The trio are credited with the discovery of several thousand asteroids.[9]
Kalchas family
Fernando Roig and Ricardo Gil-Hutton identified Kalchas as the principal body of a small Jovian asteroid family, using the hierarchical clustering method (HCM), which looks for groupings of neighboring asteroids based on the smallest distances between them in the proper orbital element space. According to the astronomers, the Kalchas family belongs to the larger Menelaus clan, an aggregation of Jupiter trojans, composed of several families, similar to the Flora family in the inner asteroid belt.[10]: 9, 10
However, this family is not included in David Nesvorný's HCM-analysis from 2014.[11] Instead, Kalchas is listed as a non-family asteroid of the Jovian background population on the Asteroids Dynamic Site (AstDyS), which is based on another analysis by Milani and Knežević.[4]
Naming
This minor planet was named from Greek mythology after Calchas, a Greek prophet during the Trojan War.[1] The Minor Planet Center published the official naming citation on 11 March 1990 (M.P.C. 16043).[12]
