A nova origin of the gas cloud at the Galactic center?

Max-Planck-Institut für Astrophysik, Karl- Schwarzschild-Str. 1, 85740 Garching, Germany
e-mail: emm@mpa-garching.mpg.de

Received: 31 July 2012
Accepted: 14 August 2012

Abstract

The recent discovery by Gillessen and collaborators of a cloud of gas falling towards the Galactic center on a highly eccentric orbit, diving nearly straight into the immediate neighborhood of the central supermassive black hole, raises the important question of its origin. Several models have already been proposed. Here we suggest that a recent nova outburst has ejected a ring-like shell of gas. Viewed at high inclination, that could account for the mass, head and tail structure, and the unusually high eccentricity of the observed cloud in a natural way, even as the nova moves on a quite normal orbit for the young stars in the close neighborhood of the Galactic center. We illustrate this by calculating orbits for the head and tail parts of the ejecta and the nova that has produced it. We briefly discuss some of the questions that this model, if true, raises about the stellar environment close to the Galactic center.