Nongravitational perturbations and virtual impactors: the case of asteroid (410777) 2009 FD Federica Spoto, Andrea Milani, Davide Farnocchia, Steven R. Chesley, Marco Micheli, Giovanni B. Valsecchi, Davide Perna and Olivier Hainaut A&A, 572 (2014) A100 Published online: 04 December 2014 DOI: 10.1051/0004-6361/201424743