128 Nemesis

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name=128 Nemesis
discoverer=James Craig Watson
discovered=November 25, 1872
alt_names=
mp_category=Main belt
epoch=December 31, 2006 (JD 2454100.5)
semimajor=411.307 Gm (2.749 AU)
perihelion=359.010 Gm (2.400 AU)
aphelion=463.605 Gm (3.099 AU)
eccentricity=0.127
period=1665.175 d (4.56 a)
inclination=6.254°
asc_node=76.457°
arg_peri=302.407°
mean_anomaly=181.168°
avg_speed=17.89 km/s
dimensions=188.2 km
mass=7.0e|18 kg
density=? g/cm³
surface_grav=0.0526 m/s²
escape_velocity=0.0995 km/s
rotation=? d
spectral_type=C
abs_magnitude=7.49
albedo=?
single_temperature=~168 K

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.