5436 Eumelos

Eumelos 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 on its orbit (see Trojans in astronomy). It orbits the Sun at a distance of 4.8–5.6 AU once every 11 years and 10 months (4,333 days; semi-major axis of 5.2 AU). Its orbit has an eccentricity of 0.08 and an inclination of 7° with respect to the ecliptic.^[3]

The body's observation arc begins with its first observation as 1986 XF₂ at the CERGA Observatory in December 1986, more than three years prior to its official discovery observation at Palomar.^[1]

Eumelos family

Fernando Roig and Ricardo Gil-Hutton identified Eumelos 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 Eumelos family belongs to the larger Menelaus clan, an aggregation of Jupiter trojans which is composed of several families, similar to the Flora family in the inner asteroid belt.^{[9]: 9, 10}

However this family is not included in David Nesvorný's HCM-analysis from 2014.^[10] Instead, Eumelos is listed as a non-family asteroid of the Jovian background population on the Asteroids Dynamic Site (AstDyS) which based on another analysis by Milani and Knežević.^[5]

This minor planet was named after Eumelus (Eumelos), son of King Admetus and leader of the Greek contingent from Pherae in the Trojan War. At funeral games for Patroclus, he was the fifth and last in the chariot races competing against Diomedes, Menelaus, Antilochus and Meriones. Though Eumelus came in last, he was awarded by Achilles with the bronze corselet stripped from the Trojan Asteropaios (see table below for the correspondingly named Jupiter trojans).^[1] The official naming citation was published by the Minor Planet Center on 12 July 1995 (M.P.C. 25444).^[11]

Euryalos is an assumed C-type asteroid, while the majority of larger Jupiter trojans are D-type asteroids.^[7]

Rotation period

In 2013, a rotational lightcurve of Eumelos was obtained from photometric observations by Linda French and Lawrence Wasserman at the Anderson Mesa Station of the Lowell Observatory, using its 0.8-meter NURO telescope over three consecutive nights until 1 March 2013. Robert Stephens at the Center for Solar System Studies in Landers, California, then observed this asteroid for five more nights during 10–14 March 2013. Lightcurve analysis gave a well-defined rotation period of 38.41±0.02 hours with a brightness amplitude of 0.68 magnitude, indicative of a non-spherical shape (U=3).^[7][8][a]

In August 2015, observations by the Kepler space telescope during its K2 mission gave two lightcurves with an alternative period of 21.23±0.37 and 21.276±0.315 hours with a brightness variation of 0.40 and 0.43 magnitude, respectively (U=2/2).^[12][13] The Collaborative Asteroid Lightcurve Link (CALL), labels the period determination for this asteroid as ambiguous.^[7]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Eumelos measures 37.70 kilometers in diameter and its surface has an albedo of 0.086,^[6] while CALL assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 46.30 kilometers based on an absolute magnitude of 10.4.^[7]

• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (5001)-(10000) – Minor Planet Center
• Asteroid 5436 Eumelos at the Small Bodies Data Ferret
• 5436 Eumelos at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 5436 Eumelos at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters