1867 Deiphobus

Deiphobus is a dark Jovian asteroid orbiting in the trailing Trojan camp at Jupiter's L₅ Lagrangian point, 60° behind its orbit in a 1:1 resonance (see Trojans in astronomy). It is a member of the Ennomos family (009),^[8] a small Jovian asteroid family with 30 known members, named after 4709 Ennomos.^[19]: 23 There only a few Jovian families known to date. The Ennomos family was first identified by Jakub Rozehnal and Miroslav Brož in 2011.^[20] However, a different HCM-based analysis assigns Deiphobus to the Jovian background population.^[7]

It orbits the Sun at a distance of 4.9–5.4 AU once every 11 years and 7 months (4,241 days; semi-major axis of 5.13 AU). Its orbit has an eccentricity of 0.04 and an inclination of 27° with respect to the ecliptic.^[4] The body's observation arc begins with its official discovery observation at Leoncito in March 1971.^[1]

Deiphobus is characterized as a dark D-type asteroid in the Tholen, Barucci, Tedesco, as well as in the SDSS-based taxonomy.^[8][15]

Several rotational lightcurve have been obtained since 1987, when the first photometric observations of Deiphobus by Linda French at CTIO indicated that the body has longer-than average rotation period of at least 24 hours.(U=2).^[5][18] In February 1994, observations by Stefano Mottola and Anders Erikson, using the ESO 1-metre telescope at La Silla Observatory in Chile, gave a slow rotation period of 58.66±0.18 hours with a brightness variation of 0.27±0.03 magnitude (U=3-).^[5][13]

Since 2015, follow-up observations by Robert Stephens at the Center for Solar System Studies measured 58.62 and 58.699, confirming Mottola's long period (U=3-/3-),^[12][14][a] and superseding other reported periods from fragmentary lightcurves (U=2/1).^[21][b]

While not being a slow rotator, Deiphobus has a much longer rotation period than the vast majority of asteroids, which typically rotate between 2 and 20 hours once around their axis. Among all large Jovian asteroids, only 617 Patroclus has a longer period than Deiphobus.

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Deiphobus measures between 118.22 and 131.31 kilometers in diameter, and its surface has an albedo between 0.037 and 0.060.^[9][10][11] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0396 and a diameter of 122.65 kilometers based on an absolute magnitude of 8.68.^[5]

This minor planet was named after the Trojan warrior, Deiphobus, son of King Priam (also see 108 Hecuba and 884 Priamus).^[3] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3935).^[22]

• Long-term evolution of asteroid families among Jovian Trojans, Jakub Rozehnal and Miroslav Brož (2014)
• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 1867 Deiphobus at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 1867 Deiphobus at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters