Black Holes: A Cavity at the Center of Our Galaxy

Black holes are one of science fiction lovers’ favorite concepts. Massively powerful, un-seeable spaces that sucks everything --light, matter, gas-- into them like milk through a straw. Fascinating. And the more that astronomers learn about black holes and how they affect our galaxies, the more fascinating they become.

Galaxies and Black Holes
You may imagine that black holes mostly live in the cold-and-empty edges of space. But in fact, black holes are the center of everything. Astronomers have discovered that every major galaxy has a black hole at its center. And while it’s not possible to study black holes sitting somewhere in the cold reaches of space, it is possible to study nearby galaxies-- and the way that black holes affect them. This is the closest scientists have ever gotten to understanding how these mind-bogglingly powerful entities wreak havoc on the space around them.

Our Very Own Black Hole
By studying other galaxies, astronomers were able to determine that supermassive black holes were galaxy-centers. But what about our own Milky Way galaxy? If our galaxy had a black hole of its own, it was a quiet one, not making the huge displays of energy seen by the black holes at the center of other galaxies. With its narrow viewing angle and the thick clouds of dust that gave our galaxy its name, even the massively powerful Hubble telescope wasn’t able to see into the center of the Milky Way.

But astronomers were determined, and in 2002 were able to convince even the most doubtful of the presence of a massive black hole at the center of the Milky Way. They did this by super-sharpening photos that tracked the paths of stars at the center of the galaxy. They found that these stars were extremely close to the center of the galaxy, and moving at 20 million miles per hour-- an incredible speed for a star. Black holes were the only answer.

Though they’ve been unable to so far, astronomers hope to soon be able to produce an image of our galaxy’s supermassive black hole by using millimeter wave telescopes. They may have an image of this cavity of space --only ten times the size of our sun but four million times the mass-- in the next ten years.

Already, astronomers are learning some amazing and startling things about how black holes work. One of the most astonishing was the discovery of a huge number of massive young stars which form close to black holes. Where other stars in the galaxy form in calm parts of space, these young stars have inexplicably formed within close reach of massive, super-powerful black holes.

Scientists are learning more and more about black holes every day. To read more about these massive black holes and how they move entire galaxies around them, visit the Smithsonian Magazine website at the following link: http://www.smithsonianmag.com/