(153591) 2001 SN263

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(153591) 2001 SN263
Discovered by LINEAR
Amor asteroid, NEO
Orbital characteristics
Epoch September 30, 2012 (JD 2456200.5)[1]
Aphelion 2.93672378 AU
Perihelion 1.03617286 AU
1.98644832 AU
Eccentricity 0.47837915
2.79978130 a
(1022.62012 d)
Inclination 6.685730°
Physical characteristics
Dimensions 2.8 km
Mass ~1.5×1013 kg
Mean density
1.3±0.6 g/cm³
0.045 cm/s²
110 cm/s
3.423 h
Albedo 0.05
Spectral type

(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,[2] 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[edit]

The orbital properties of the satellites are listed in this table.[3] 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
Gamma (inner) ~10×1010 3.8 0.686 0.016
Beta (outer) ~24×1010 16.6 6.225 0.015


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