15094 Polymele


15094 Polymele is a primitive Jupiter trojan from the Greek camp, approximately in diameter. It is a target of the Lucy mission with a close fly by planned to occur in September 2027. It was discovered on 17 November 1999, by astronomers with the Catalina Sky Survey at Mount Lemmon Observatory, Arizona, in the United States. The P-type asteroid has a rotation period of 5.9 hours and possibly a spherical shape. It was named after Polymele from Greek mythology, the wife of Menoetius and the mother of Patroclus.

Orbit and classification

Polymele is a Jupiter trojan orbiting in the leading Greek camp at Jupiter's Lagrangian point, 60° ahead of the Gas Giant's orbit . It orbits the Sun at a distance of 4.7–5.7 AU once every 11 years and 9 months. Its orbit has an eccentricity of 0.09 and an inclination of 13° with respect to the ecliptic. The asteroid's observation arc begins 48 years prior to its official discovery observation at Mount Lemmon, with a precovery taken at Palomar Observatory in 1951, and published by the Digitized Sky Survey later on.

Naming

This minor planet was named after Polymele, the daughter of Peleus from Greek mythology. According to the Latin author Gaius Julius Hyginus, she is the wife of the Argonaut Menoetius and the mother of Patroclus, who participated in the Trojan War. Polymele is also known as "Philomela"; that name was previously used for the asteroid 196 Philomela. The approved naming citation was published by the Minor Planet Center on 22 February 2016.

''Lucy'' mission target

Polymele is planned to be visited by the Lucy spacecraft which will launch in 2021. The fly by is scheduled for 15 September 2027, and will approach the asteroid to a distance of 415 kilometers at a velocity of 6 kilometers per second. The mission's targets with their flyby dates are:
Polymele has been characterized as a primitive P-type asteroid by the investigators of the Lucy mission. P-type asteroids are known for their low albedo. It has a V–I color index of 0.799, which is lower than that for most larger Jupiter trojans .

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Polymele measures 21.075 kilometers in diameter and its surface has an albedo of 0.091, while in 2018, Marc Buie published an albedo of 0.073 and an absolute magnitude of 11.691 in the S- and/or R band. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a larger diameter of 26.64 kilometers based on an absolute magnitude of 11.6.

Lightcurves

In March 2016, a rotational lightcurve of Polymele was obtained from photometric observations by Marc Buie and colleges. Lightcurve analysis gave a rotation period of hours with a small brightness amplitude of magnitude, which indicates that the body has a spheroidal shape. Previously, the Lucy mission team published spin rates of 6.1 and 4 hours, respectively.