title: Binary asteroids in the near-Earth object population.
abstract: Radar images of near-Earth asteroid 2000 DP107 show that it is composed of an approximately 800-meter-diameter primary and an approximately 300-meter-diameter secondary revolving around their common center of mass. The orbital period of 1.755 +/- 0.007 days and semimajor axis of 2620 +/- 160 meters constrain the total mass of the system to 4.6 +/- 0.5 x 10(11) kilograms and the bulk density of the primary to 1.7 +/- 1.1 grams per cubic centimeter. This system and other binary near-Earth asteroids have spheroidal primaries spinning near the breakup point for strengthless bodies, suggesting that the binaries formed by spin-up and fission, probably as a result of tidal disruption during close planetary encounters. About 16% of near-Earth asteroids larger than 200 meters in diameter may be binary systems.
authors.affiliation: California Institute of Technology, MC 150-21, Pasadena, CA 91125, USA. margot@gps.caltech.edu
authors.forename: J L
authors.initials: JL
authors.lastname: Margot
authors.forename: M C
authors.initials: MC
authors.lastname: Nolan
authors.forename: L A M
authors.initials: LA
authors.lastname: Benner
authors.forename: S J
authors.initials: SJ
authors.lastname: Ostro
authors.forename: R F
authors.initials: RF
authors.lastname: Jurgens
authors.forename: J D
authors.initials: JD
authors.lastname: Giorgini
authors.forename: M A
authors.initials: MA
authors.lastname: Slade
authors.forename: D B
authors.initials: DB
authors.lastname: Campbell