Preparing for Fireworks in Our Galactic Center

NASA's Nuclear Spectroscopic Telescope Array captured these views of the supermassive black hole at the heart of our galaxy in high-energy X-rays. The background image, taken in infrared light, shows the location of our Milky Way's supermassive black hole. In the main image, the brightest white dot is the hottest material located closest to the black hole, and the surrounding pinkish blob is hot gas, likely belonging to a nearby supernova remnant. The time series at right shows observed flaring at four different X-ray energies. A gas cloud has been spotted approaching the black hole, and new calculations predict that bright radio emission from shocks generated buy this encounter may be detected later this year.

 The super-massive black hole at the center of the Milky Way, however, is quiescent. It emits no jets, and matter around the source has been seen only faintly spotted. The larger volume around the black hole, however, is much busier. There are seven bright stars and perhaps a thousand fainter stars orbiting the black hole, along with hot gas and dust. Over the years astronomers have measured the orbital motions of the bright stars to determine the mass of the black hole to a precision of about 10%. About ten years ago scientists noticed what seemed to be a cloud of gas also in orbit near the black hole. Last year they announced that, if their calculations are correct, the gas cloud will approach extremely close to the black hole -- about thirty-six light-hours (about 260 astronomical units) - and will do so sometime later this year! No one knows for sure what will happen, but some dramatic fireworks are expected if the cloud is torn apart by the strong gravitational force of the black hole, or is even eaten.