The presence of massive young stars very close (0.1 pc) to the Galactic centre challenges star formation theories: stars should not be able to form this close to the supermassive black hole, due to tidal shearing of the molecular cloud, and they should not be able to travel from elsewhere to the Galactic centre to still be young when they get there. Bonnell and Rice (arXiv:0810.2723) have done some numerical simulations showing the infall of a giant molecular cloud that interacts with the black hole. They show that part of the cloud becomes bound to the black hole and forms an eccentric disk which fragments to form stars (as shown in above figure). This process can explain the observed rings of massive young stars at the Galactic centre.
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