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] | |
---|---|
Discovered by | Spacewatch |
Discovery site | Kitt Peak Obs. |
Discovery date | 25 September 1990 |
Designations | |
1990 SS | |
Pronunciation | /sʌˈmeɪnəs/[2] |
Named after | Summānus |
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 |
1.7035 AU | |
Eccentricity | 0.4746 |
2.22 yr (812 days) | |
346.75° | |
0° 26m 35.88s / day | |
Inclination | 19.419° |
359.89° | |
116.07° | |
Earth MOID | 0.0689 AU (26.8 LD) |
Physical characteristics | |
Mean diameter | 1.298±0.446 km[3] |
7.358 h[4] | |
0.033±0.029[3] | |
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).