78 Diana

Diana (minor planet designation: 78 Diana) is a large and dark main-belt asteroid. It was discovered by German astronomer Robert Luther on March 15, 1863, and named after Diana, Roman goddess of the hunt. The asteroid is orbiting the Sun at a distance of 391.934 Gm with a period of 4.24 years and an eccentricity (ovalness) of 0.207. The orbital plane is tilted at an angle of 8.688° relative to the plane of the ecliptic. Its composition is carbonaceous and primitive.

Photometric observations of this asteroid during 1986 and 2006–08 gave a light curve with a rotation period of 7.2991 hours and a brightness variation in the range 0.02–0.104 magnitude. Based upon radar data, the near surface solid density of the asteroid is 2.7 $123.63 km$ g cm−3. 78 Diana occulted a star on September 4, 1980. A diameter of 116 km was measured, closely matching the value given by the IRAS satellite.

Diana is expected to pass about 0.003 AU from (29075) 1950 DA on August 5, 2150. Main-belt asteroid 4217 Engelhardt (~9 km in diameter) will pass about 0.0017 AU from (29075) 1950 DA in 2736.