Discovered by James Craig Watson Pronunciation /ˈnɛmᵻsɪs/ Observation arc 143.39 yr (52373 d) Orbits Sun Discoverer James Craig Watson Named after Nemesis | Discovery date 25 November 1872 Minor planet category Main belt, Discovered 25 November 1872 Spectral type C-type asteroid Asteroid family Nemesis family | |
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Aphelion 3.09824 AU (463.490 Gm) Similar James Craig Watson discoveries, Other celestial objects | ||
128 nemesis is here
128 Nemesis is a large 188 km main-belt asteroid, of carbonaceous composition. It rotates rather slowly, taking about one and half Earth days (39 hours) 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 was also the name of a hypothetical companion star of the Sun, which does not exist.
It is categorized as a C-type asteroid, indicating a primitive carbonaceous composition. Based on IRAS data Nemesis is about 188 km in diameter and is around the 33rd largest main-belt asteroid. The 39‑hour rotation period is the second longest for an asteroid more than 150 km in diameter.