9694 Lycomedes

9694 Lycomedes

Shape model of Lycomedes from its lightcurve
Discovery [1]
Discovered by	C. J. van Houten I. van Houten-G. T. Gehrels
Discovery site	Palomar Obs.
Discovery date	26 September 1960
Designations
MPC designation	(9694) Lycomedes
Pronunciation	/lɪkəˈmiːdiːz/[2]
Named after	Lycomedes [1] (Greek mythology)
Alternative designations	6581 P-L · 1990 DY1
Minor planet category	Jupiter trojan [1][3] Greek [4] · background [5]
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	57.65 yr (21,058 d)
Aphelion	5.2852 AU
Perihelion	4.9135 AU
Semi-major axis	5.0993 AU
Eccentricity	0.0364
Orbital period (sidereal)	11.52 yr (4,206 d)
Mean anomaly	226.07°
Mean motion	0° 5m 8.16s / day
Inclination	4.9436°
Longitude of ascending node	350.07°
Argument of perihelion	53.908°
Jupiter MOID	0.019 AU
TJupiter	2.9920
Physical characteristics
Mean diameter	31.74±0.24 km[6] 40.33 km (calculated)[7]
Synodic rotation period	18.2±0.1 h[8]
Geometric albedo	0.057 (assumed)[7] 0.101±0.010[6]
Spectral type	C (assumed)[7]
Absolute magnitude (H)	10.60[6] 10.7[1][3][7]

9694 Lycomedes /lɪkəˈmiːdiːz/ is a Jupiter trojan from the Greek camp, approximately 32 kilometers (20 miles) in diameter.^[1] It was discovered during the Palomar–Leiden survey at the Palomar Observatory in 1960 and later named after Lycomedes from Greek mythology.^[1] The dark Jovian asteroid is likely elongated in shape and has a rotation period of 18.2 hours.^[7]

Lycomedes was discovered on 26 September 1960, by Dutch astronomer couple Ingrid and Cornelis van Houten at Leiden, on photographic plates taken by astronomer Tom Gehrels at the Palomar Observatory in California.^[1] The body's observation arc begins the night after its official discovery observation at Palomar.^[1]

The survey designation "P-L" stands for "Palomar–Leiden", named after Palomar and Leiden observatories, which collaborated on the fruitful Palomar–Leiden survey in the 1960s. 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]

This minor planet was named from Greek mythology after Lycomedes, the Greek king of Scyros. At the request of Thetis, he concealed her son Achilles dressed in girl's clothes among his own daughters to save him from the Trojan War until Odysseus drew him out of his disguise.^[1] The official naming citation was published by the Minor Planet Center on 2 April 1999 (M.P.C. 34355).^[10]

As all Jupiter trojans, Lycomedes is 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).^[4]

It orbits the Sun at a distance of 4.9–5.3 AU once every 11 years and 6 months (4,206 days; semi-major axis of 5.1 AU). Its orbit has an eccentricity of 0.04 and an inclination of 5° with respect to the ecliptic.^[3]

Lycomedes is an assumed C-type asteroid, while most larger Jupiter trojans are D-types.^[7]

In October 2010, a first rotational lightcurve of Lycomedes was obtained from photometric observations by astronomers at the Palomar Transient Factory in California. Lightcurve analysis gave a rotation period of 18.090±0.0211 hours with a brightness amplitude of 0.38 magnitude (U=2).^[7][11]

In November 2011, follow-up observations over two consecutive nights were made by Daniel Coley at the Goat Mountain Astronomical Research Station (G79) in California. It gave a concurring rotation period of 18.2±0.1 hours with a high brightness amplitude of 0.55 magnitude, indicative of a non-spherical shape (U=2).^[8][a]

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Lycomedes measures between 31.736 and 31.74 kilometers in diameter and its surface has an albedo,^[6] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 40.33 kilometers based on an absolute magnitude of 10.7.^[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 9694 Lycomedes at the Small Bodies Data Ferret
• 9694 Lycomedes at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 9694 Lycomedes at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters