Spiral galaxies, like our own Milky Way, have that familiar disk shape, with a thick central bulge and spiral arms spinning outward like a pinwheel. Our own Sun is pretty far away from the galaxy center, and that’s a good thing. The center of galaxies is a dangerous place with lots of radiation, and a supermassive black hole gobbling up everything that falls into it.
In our own Milky Way, the galactic center is located about 25,000 light-years from Earth in the constellation Sagittarius. Unfortunately, the center of the galaxy is obscured by interstellar dust that blocks visible light, so it can’t be studied in many wavelengths. Fortunately, infrared radiation passes right through this dust, and so astronomers have been able to study the size and mass of our galaxy center, and locate the supermassive black hole lurking at the very middle of the galaxy.
Sagittarius A* is located at the very middle of the galaxy, and gives off a large amount of radio waves. This is our galaxy’s supermassive black hole, with millions of times the mass of the Sun. Within a parsec of Sag A*, there are thought to be thousands of stars; most of these are old red stars, but there are many massive stars there too. In fact, the center of the galaxy resembles an irregular galaxy.
Star formation doesn’t seem to be happening in the galaxy center, but astronomers predict that conditions could be right in about 200 million years to ignite a new phase of star formation.
While we can’t see the center of our own galaxy, there are many other galaxies out there for us to study; many of them are face-on. By examining them, we can understand our own galaxy much better.
We have written many articles about the galaxies for Universe Today. Here’s an article about how the supermassive black hole in our galaxy is starving, and here’s article about a galaxy with a warped disk around its center.
We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.