The Invisible Janitor at the Heart of the Milky Way
At the center of the Milky Way, 27,000 light-years from Earth, lives the supermassive black hole Sagittarius A*. It weighs in at four million Suns. It does not flare brightly like quasars; instead, it smolders almost imperceptibly. For a long time, astronomers debated whether it blows a wind. Now we have the answer: it does.