11885 Summanus (prov. designation: 1990 SS) is a dark asteroid and large near-Earth object of the Apollo group. It was discovered by astronomers with the Spacewatch programm at Kitt Peak Observatory on 25 September 1990. The object has a rotation period of 7.3 hours and measures approximately 1.3 kilometers (0.8 miles) in diameter.[3] It was named after Summanus, the Roman deity of nocturnal lightning and thunder.[1]
Discovery[1] | |
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Discovered by | Spacewatch |
Discovery site | Kitt Peak Obs. |
Discovery date | 25 September 1990 |
Designations | |
MPC designation | 1990 SS |
Pronunciation | /sʌˈmeɪnəs/[2] |
Named after | Summānus |
Minor planet category | NEO · Apollo[3] |
Orbital characteristics[3] | |
Epoch 4 September 2017 (JD 2458000.5) | |
Uncertainty parameter 0 | |
Observation arc | 20.54 yr (7,504 days) |
Aphelion | 2.5119 AU |
Perihelion | 0.8950 AU |
Semi-major axis | 1.7035 AU |
Eccentricity | 0.4746 |
Orbital period (sidereal) | 2.22 yr (812 days) |
Mean anomaly | 346.75° |
Mean motion | 0° 26m 35.88s / day |
Inclination | 19.419° |
Longitude of ascending node | 359.89° |
Argument of perihelion | 116.07° |
Earth MOID | 0.0689 AU (26.8 LD) |
Physical characteristics | |
Mean diameter | 1.298±0.446 km[3] |
Synodic rotation period | 7.358 h[4] |
Geometric albedo | 0.033±0.029[3] |
Absolute magnitude (H) | 18.5[3] |
Summanus was discovered on 25 September 1990, by Spacewatch survey at the Kitt Peak Observatory, southwest of Tucson, Arizona, United States. It was the first fully automatic discovery of a near-Earth asteroid.[5][6] The name Summanus is symbolic of the discovery of the asteroid by software running on a (lightning-fast) computer.[1]
The orbit is well-established with over 20 years of observations. Summanus orbits the Sun in the inner main-belt at a distance of 0.9–2.5 AU once every 2 years and 3 months (812 days). Its orbit has an eccentricity of 0.47 and an inclination of 19° with respect to the ecliptic.[3]
The closest approach to the Earth in the years 1900–2200 is 0.102 AU (15,300,000 km; 9,500,000 mi) on 17 March 1991, and 17 March 2011. For comparison, the distance to the Moon is about 0.0026 AU (390,000 km; 240,000 mi).
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