The Galactic Center!

Our galaxy is a pretty cool place. It may not be anything special, but it's home and it's ours, and that's good enough for me. Even though the Milky Way is pretty normal, there are still some pretty strange things going on.

Take, for example, our galactic center. As one might expect, it's a pretty crowded, busy space: there are lots of stars that interact with each other often. In fact, if you lived on a planet close to the galactic center, the total intensity of light from stars would be the equivalent of 200 of our full moons. Basically, night as we know it, would never occur. Amid all this brightness, however, is the darkest object that can exist, as far as we know: a supermassive black hole, millions of times more massive than our Sun.

Sagittarius A* (you say, "A star"), as far as we can tell, is very, very close to the galactic center. Hundreds of stars crowd within one light year of Sagittarius A* (in most of the galaxy, the average distance from from star to star is one light year). Sagittarius A* doesn't actually appear in infrared images. Scientists, however, have been using infrared observations to make alarming and astonishing discoveries.

Scientists have found a large number of stars orbiting around Sagittarius A* at speeds of over 1500 km/s (for comparison, the Earth orbits the Sun at 30 km/s)! It has also been found that stars have incredibly small elliptical orbits, within 45 AU, or about 1.5 times the distance from the Sun to Neptune.

Sagittarius A* must exert an incredibly powerful gravitational force to keep stars in such small, rapid orbits. Using Newton's form of Kepler's third law to stars that orbit Sagittarius A*, scientists have discovered that whatever it is, Sagittarius A* would have to be 3.7 million solar masses.

Sagittarius A* can only be one thing: a supermassive black hole.


Cue Muse's "Supermassive Black Hole." It doesn't have anything to do with Astronomy, but it is damn catchy.