Black hole's burps may blow bubbles around Milky Way

STARS plunging into the giant black hole at the centre of our galaxy can explain two huge bubbles of gamma rays that NASA's Fermi space telescope discovered last year. The bubbles tower 25,000 light years above and below the Milky Way's disc of stars.  More than 100,000 stars swarm within a light year of the black hole. Now, Kwong Sang Cheng of the University of Hong Kong and his colleagues calculate that the black hole's gravity tears one of these stars apart every 30,000 years (The Astrophysical Journal Letters, in press). Half the star's mass falls into the black hole, while the other half shoots away at high speed, shocking gas that lies in the halo around the Milky Way's disc until it emits gamma rays.   link