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511 Davida
511 Davida is a large C-type asteroid in the asteroid belt. It was discovered by R. S. Dugan in 1903. It is one of the ten most-massive asteroids, and the 7th-largest asteroid. It is approximately 270–310 km in diameter and comprises an estimated 1.5% of the total mass of the asteroid belt.〔〔"Baer Mass of 511 Davida" 0.220 / "Mass of Mbelt" 15 = 0.0146〕 It is a C-type asteroid, which means that it is dark in colouring with a carbonaceous chondrite composition.
Davida is one of the few main-belt asteroids whose shape has been determined by ground-based visual observation. From 2002 to 2007, astronomers at the Keck Observatory used the Keck II telescope, which is fitted with adaptive optics, to photograph Davida. The asteroid is not a dwarf planet: there are at least two promontories and at least one flat facet with 15-km deviations from a best-fit ellipsoid. The facet is presumably a 150-km global-scale crater like the ones seen on 253 Mathilde. Conrad et al. (2007) show that craters of this size "can be expected from the impactor size distribution, without likelihood of catastrophic disruption of Davida."
Davida is named after David Peck Todd, an astronomy professor at Amherst College.
== Mass ==
In 2001, Michalak estimated Davida to have a mass of () kg〔() solar masses, per Michalak (2001), extended dynamic model.〕 In 2007, Baer and Chesley estimated Davida to have a mass of () kg. , Baer suggests Davida has a mass of () kg. This most recent estimate by Baer suggests that Davida is less massive than 704 Interamnia, making Davida the sixth-most-massive asteroid, though the error bars overlap.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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