Abstract：
:Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process may explain their formation-critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation.
journal_name
Naturejournal_title
Natureauthors
Pravec P,Vokrouhlický D,Polishook D,Scheeres DJ,Harris AW,Galád A,Vaduvescu O,Pozo F,Barr A,Longa P,Vachier F,Colas F,Pray DP,Pollock J,Reichart D,Ivarsen K,Haislip J,Lacluyze A,Kusnirák P,Henych T,Marchis F,Macdoi
10.1038/nature09315subject
Has Abstractpub_date
2010-08-26 00:00:00pages
1085-8issue
7310eissn
0028-0836issn
1476-4687pii
nature09315journal_volume
466pub_type
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