Deiphobus is a dark Jovian asteroid orbiting in the trailing Trojan camp at Jupiter's Lagrangian point, 60° behind its orbit in a 1:1 resonance. It is a member of the Ennomos family, a small Jovian asteroid family with 30 known members, named after 4709 Ennomos. There only a few Jovian families known to date. The Ennomos family was first identified by Jakub Rozehnal and Miroslav Brož in 2011. However, a different HCM-based analysis assigns Deiphobus to the Jovian background population. It orbits the Sun at a distance of 4.9–5.4 AU once every 11 years and 7 months. Its orbit has an eccentricity of 0.04 and an inclination of 27° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Leoncito in March 1971.
Physical characteristics
Deiphobus is characterized as a dark D-type asteroid in the Tholen, Barucci, Tedesco, as well as in the SDSS-based taxonomy.
Lightcurves
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.. 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 hours with a brightness variation of magnitude. 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, and superseding other reported periods from fragmentary lightcurves. 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 SatelliteIRAS, 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. 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.
