878 Mildred is aminor planet in themain belt orbiting theSun. It is the lowest numbered, and thus the namesake, of the Mildred family of asteroids, a subgroup of theNysa family.[3] The Mildred subgroup, and by extension 878 Mildred itself, is thought to have been formed by a recent fragmentation event from a larger asteroid.[3]
878 Mildred was originally discovered in 1916 using the 1.5 m Hale Telescope at theMount Wilson Observatory, but was subsequently lost until it was again observed on single nights in 1985 and 1991 (alost asteroid).[2] Initially only two observations of the asteroid were taken on 1916-09-06 which does not allow for an accurate orbital determination, however interest in the object prompted further investigation and more measurements were taken in late September and October.[4] The asteroid was re-discovered in 1991 byGareth V. Williams.[5] It is named afterMildred Shapley Matthews.
By comparing the asteroid's perceived brightness and the then computed distance from the Sun they arrived at anabsolute visual magnitude of 14.3, which if one assumesMars-like albedo gives an approximate diameter of 3 to 5 kilometers.[4]