The image has been smoothed to bring out the X-ray emission from an extended cloud of hot gas surrounding the supermassive black-hole candidate Sagittarius A* (larger white dot at the very center of the image- a little to the left and above the smallest white dot). This gas glows in X-ray light because it has been heated to a temperature of millions of degrees by shock waves produced by supernova explosions and perhaps by colliding winds from young massive stars.