title: Retrograde spins of near-Earth asteroids from the Yarkovsky effect.
abstract: Dynamical resonances in the asteroid belt are the gateway for the production of near-Earth asteroids (NEAs). To generate the observed number of NEAs, however, requires the injection of many asteroids into those resonant regions. Collisional processes have long been claimed as a possible source, but difficulties with that idea have led to the suggestion that orbital drift arising from the Yarkovsky effect dominates the injection process. (The Yarkovsky effect is a force arising from differential heating-the 'afternoon' side of an asteroid is warmer than the 'morning' side.) The two models predict different rotational properties of NEAs: the usual collisional theories are consistent with a nearly isotropic distribution of rotation vectors, whereas the 'Yarkovsky model' predicts an excess of retrograde rotations. Here we report that the spin vectors of NEAs show a strong and statistically significant excess of retrograde rotations, quantitatively consistent with the theoretical expectations of the Yarkovsky model.
authors.affiliation: Dipartimento di Matematica, Università di Pisa, via Buonarroti 2, I-56127 Pisa, Italy.
authors.forename: A
authors.initials: A
authors.lastname: La Spina
authors.forename: P
authors.initials: P
authors.lastname: Paolicchi
authors.forename: A
authors.initials: A
authors.lastname: Kryszczyńska
authors.forename: P
authors.initials: P
authors.lastname: Pravec