In the
Tholen classification, Troilus has an ambiguous and unusual spectrum, closest to that of an
F-type and somewhat similar to a common
C-type asteroid (FCU). It has also been characterized as a carbonaceous C-type in the Barucci taxonomy (C0-type).
Rotation period In April 2007, a rotational
lightcurve of Troilus was obtained from
photometric observations by
Lawrence Molnar at the
Calvin-Rehoboth Robotic Observatory in New Mexico. Lightcurve analysis gave a
rotation period of hours with a brightness variation of
magnitude (). While not being a slow rotator,
Troilus has a significantly longer period than most asteroids, and one of longest of all larger Jupiter trojans. The period also supersedes previous observations made by Linda French with the
0.9-meter SMARTS telescope at
Cerro Tololo in the 1980s and by Federico Manzini at the Sozzago Astronomical Station , which gave a period of 24 and 63.8 hours, respectively ().
Diameter and albedo According to the surveys carried out by the Infrared Astronomical Satellite
IRAS, the Japanese
Akari satellite and the
NEOWISE mission of NASA's
Wide-field Infrared Survey Explorer, Troilus measures between 100.48 and 111.36 kilometers in diameter and its surface has an
albedo between 0.037 and 0.0419. The
Collaborative Asteroid Lightcurve Link derives an albedo of 0.0397 and a diameter of 103.31 kilometers based on an
absolute magnitude of 9.05. == Naming ==