| Discovery | |
|---|---|
| Discovered by: | James Craig Watson |
| Discovery date: | November 25, 1872 |
| Orbital characteristics | |
| Epoch December 31, 2006 (JD 2454100.5) | |
| Aphelion | 463.605 Gm (3.099 AU) |
| Perihelion: | 359.010 Gm (2.400 AU) |
| Semi-major axis: | 411.307 Gm (2.749 AU) |
| Eccentricity: | 0.127 |
| Orbital period: | 1665.175 d (4.56 a) |
| Avg. orbital speed: | 17.89 km/s |
| Mean anomaly: | 181.168° |
| Inclination: | 6.254° |
| Longitude of ascending node: | 76.457° |
| Argument of perihelion: | 302.407° |
| Physical characteristics | |
| Dimensions: | 188.2 km |
| Mass: | 7.0×1018 kg |
| Mean density: | ? g/cm³ |
| Equatorial surface gravity: | 0.0526 m/s² |
| Escape velocity: | 0.0995 km/s |
| Rotation period: | ? d |
| Albedo: | ? |
| Temperature: | ~168 K |
| Spectral type: | C |
| Absolute magnitude: | 7.49 |
128 Nemesis is a very large and very dark main belt asteroid, of carbonaceous composition. It rotates rather slowly, taking about one and half Earth days to complete one revolution. Nemesis is the largest member of the Nemesian asteroid family bearing its name. It was discovered by J. C. Watson on November 25, 1872 and named after Nemesis, the goddess of retribution in Greek mythology. Nemesis is also the name of a hypothetical companion star of the sun.
| Minor planets (see full list) |
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| Previous minor planet | 128 Nemesis | Next minor planet |
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| Vulcanoids · Near-Earth asteroids · Main belt · Jupiter Trojans · Centaurs · Damocloids · Neptune Trojans · Comets · Trans-Neptunians (Kuiper belt • Scattered disc objects • Oort cloud) |
| For other objects and regions, see Asteroid groups and families, Binary asteroids, Asteroid moons, meteoroids and the Solar System. For a complete listing, see List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names. |
