128 Nemesis

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.