|Discovered by S. Ueda
MPC designation (5646) 1990 TR
Minor planet category Amor · NEO
Discovered 11 October 1990
Asteroid group Amor asteroid
|Discovery date 11 October 1990|
Alternative names 1990 TR
Observation arc 26.75 yr (9,769 days)
Absolute magnitude 15.2
Discovery site Kushiro Observatory
|Discoverers Hiroshi Kaneda, Seiji Ueda|
Similar 3671 Dionysus, Sun, Solar System, 1862 Apollo, (285263) 1998 QE2
(5646) 1990 TR is a probable rare-type binary asteroid classified as near-Earth object of the Amor group, approximately 2.3 kilometers in diameter. It was discovered on 11 October 1990, by Japanese astronomers Seiji Ueda and Hiroshi Kaneda at Kushiro Observatory () near Kushiro, in eastern Hokkaido, Japan.
The asteroid orbits the Sun at a distance of 1.2–3.1 AU once every 3 years and 2 months (1,146 days). Its orbit has an eccentricity of 0.44 and an inclination of 8° with respect to the ecliptic. The body's observation arc begins with its first observation at the Siding Spring Observatory, five months prior to its official discovery observation at Kushiro.
In December 2012, the so far best rated rotational lightcurve was obtained by American astronomer Brian Warner at his Palmer Divide Observatory in Colorado. Lightcurve analysis gave a rotation period of 3.1999 hours with a brightness variation of 0.12 magnitude (U=3). Photometric observations also gave a period of 19.47 hours for a probable asteroid moon, with a measured diameter-ratio of 6999180000000000000♠0.18±0.02, which translates into a diameter of 400 meters for its moon.
According to the surveys carried out by the Spitzer Space Telescope and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures 2.03 and 2.723 kilometers in diameter and its surface has an albedo of 0.19 and 0.66. The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.18 and derives a diameter of 2.3 kilometers based on an absolute magnitude of 15.67.