| Minorplanet: | yes |
| 11885 Summanus | |
| Background: |
|
| Discovered: | 25 September 1990 |
| Pronounced: | [1] |
| Epoch: | 4 September 2017 (JD 2458000.5) |
| Uncertainty: | 0 |
| Observation Arc: | 20.54 yr (7,504 days) |
| Perihelion: | 0.8950 AU |
| Semimajor: | 1.7035 AU |
| Eccentricity: | 0.4746 |
| Period: | 2.22 yr (812 days) |
| Mean Motion: | / day |
| Inclination: | 19.419° |
| Asc Node: | 359.89° |
| Arg Peri: | 116.07° |
| Moid: | 0.0689AU |
| Abs Magnitude: | 18.5 |
11885 Summanus (prov. designation:) 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 1.3km (00.8miles) in diameter. It was named after Summanus, the Roman deity of nocturnal lightning and thunder.
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. The name Summanus is symbolic of the discovery of the asteroid by software running on a (lightning-fast) computer.
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.
The closest approach to the Earth in the years 1900–2200 is 0.102abbr=onNaNabbr=on on 17 March 1991, and 17 March 2011. For comparison, the distance to the Moon is about 0.0026abbr=onNaNabbr=on.