Chandra image of light echoes near galactic center
Credit:NASA/CXC/Caltech/M.Muno et al.

Echoes of a Monster's Roar

The center of the Milky Way harbors a monstrous black hole, a few million times more massive than the Sun, called Sgr A*. It's usually hibernating and not particularly active. Every once in a while, though, the monster wakes up to feed. The activity shows up as violent brightenings of Sgr A*. But these outbursts can be so powerful the ripples of light themselves can be detected. Astronomers have directly imaged these echos using the Chandra X-ray observatory. In the Chandra X-ray image above, Sgr A* is marked by an arrow, and appears as a rather non-descript point of X-ray light. The ellipses mark cold clouds of gas which are surprisingly bright in X-rays. Surprising because X-rays are usually associated only with very hot or very energetic objects, not cold clouds. Also surprising because the emission is variable, as shown by the inset images. This variable light emission must be due to a reflection of a brightening of Sgr A*, delayed by the enormous light travel time distance between Sgr A* and the clouds.

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Page Author: Dr. Michael F. Corcoran
Last modified Friday, 20-Apr-2012 15:25:29 EDT

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