Image in TIFF format (2127 Kb)
This false colour picture shows the region near the centre of the Milky Way as seen by Integral in gamma rays. The position of the super-massive black hole Sgr A* and of the molecular cloud Sgr B2 are indicated. The projected distance between Sgr A* and Sgr B2 is approximately 350 light years. Only now is Sgr B2 being exposed to the gamma rays emitted by Sgr A* 350 years ago, during one of its 'high' states. This powerful radiation is absorbed and then re-emitted by the molecular hydrogen gas in Sgr B2, which becomes fluorescent in the gamma rays. The other bright objects on the right-hand side of the picture are known gamma ray emitters.
Click here for animation in WMV format
This animation shows what astronomers believe has happened in the past near the centre of the Milky Way. A strong burst of gamma rays, emitted by Sgr A* about 350 years ago and lasting several years, has travelled through space and has now reached Sgr B2, a cloud of molecular hydrogen gas. The powerful gamma ray energy lightens up the gas, which absorbs and then re-emits the radiation it receives. Studying the radiation reflected by Sgr B2 has allowed astronomers to reconstruct for the first time in detail the hectic past of Sgr A*.