| Minorplanet: | yes |
| 161989 Cacus | |
| Background: |
|
| Discovered: | 8 February 1978 |
| Mpc Name: | (161989) Cacus |
| Alt Names: | 1978 CA |
| Epoch: | 4 September 2017 (JD 2458000.5) |
| Uncertainty: | 0 |
| Observation Arc: | 38.59 yr (14,096 days) |
| Perihelion: | 0.8828 AU |
| Semimajor: | 1.1231 AU |
| Eccentricity: | 0.2140 |
| Period: | 1.19 yr (435 days) |
| Mean Motion: | / day |
| Inclination: | 26.060° |
| Asc Node: | 161.24° |
| Arg Peri: | 102.16° |
| Mean Diameter: | km km km |
| Rotation: | h h h |
| Albedo: | 0.119 |
| Spectral Type: | Tholen SQ B–V 0.910 U–B 0.484 |
| Abs Magnitude: | 16.5817.117.217.3217.43 |
161989 Cacus (prov. designation:) is a stony asteroid, classified as near-Earth object and a potentially hazardous asteroid of the Apollo group, approximately 1 kilometer in diameter. It was discovered on 8 February 1978, by German astronomer Hans-Emil Schuster at ESO's La Silla Observatory in northern Chile. Its orbit is confined between Venus and Mars.
This minor planet was named from Roman mythology, after Cacus, a fire-breathing monster, which was killed by Hercules. The official naming citation was published by the Minor Planet Center on 24 November 2007 .
| 1941-09-02 | ± 6 km | ||
| 2022-09-01 | ± 21 km |