Discovered by LINEAR Minor planet category Amor asteroid, NEO Discovered 20 September 2001 Argument of perihelion 172.86251° Asteroid group Amor asteroid | Discovery date 20 September 2001 Observation arc 9198 days (25.18 yr) Inclination 6.6857915° Mean anomaly 297.35982° | |
Aphelion 2.93738213 AU (439.426112 Gm) Semi-major axis 1.98683166 AU (297.225786 Gm) Discoverer Lincoln Near-Earth Asteroid Research Similar (136617) 1994 CC, Solar System, (66391) 1999 KW4, (47171) 1999 TC36, (175706) 1996 FG3 | ||
(153591) 2001 SN263 is a small near-Earth asteroid discovered by the LINEAR project in 2001. In 2008, scientists using the planetary radar at Arecibo Observatory discovered that the object is orbited by two satellites, when the triple asteroid made a close approach to Earth of 0.066 AU (nearly 10 million kilometers). The largest body is called Alpha and is spheroid in shape, with principal axes of 2.8±.1 km, 2.7±.1 km, and 2.5±.2 km and a density of nearly 1.3±0.6 g cm−3, and the satellites, named Beta and Gamma, are several times smaller in size. Beta is 1.1 km in diameter and Gamma 0.4 km.
The only other unambiguously identified triple asteroid in the near-Earth population is (136617) 1994 CC, which was discovered to be a triple system in 2009.
Orbital characteristics of satellites
The orbital properties of the satellites are listed in this table. The orbital planes of both satellites are inclined relative to each other; the relative inclination is about 14 degrees. Such a large inclination is suggestive of past evolutionary events (e.g. close encounter with a terrestrial planet, mean-motion-resonance crossing) that may have excited their orbits from a coplanar configuration to an inclined state.