(153591) 2001 SN263
|Amor asteroid, NEO|
|Epoch September 30, 2012 (JD 2456200.5)|
(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.
|Name||Mass [kg]||Semi-major axis [km]||Orbital period [days]||Eccentricity|
- Robert Roy Britt, Triple Asteroid Found Near Earth, Space.com, 13 Feb 2008
- Emily Lakdawalla, Triple Near-Earth Asteroid Discovered The Planetary Society, 13 Feb 2008
- Images of the asteroid and its moons
- Julia Fang, "Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution", 
- A Lander to Investigate a C-type Triple Near-Earth Asteroid System: 2001 SN263
- http://adsabs.harvard.edu/abs/2008DPS....40.2806B Physical Modeling of Triple Near-Earth Asteroid 153591 (2001 SN263)
- Fang, Julia. "Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution". Astronomical Journal. Retrieved 8 November 2012.