Milky Way’s Heart III
More than three decades ago, astronomers discovered that gas was swirling around a dark, massive object at the center of our home galaxy, the Milky Way. The most likely explanation was a black hole a few million times as massive as the Sun.
But they couldn’t nail down that explanation until the last few years. The galaxy’s hub is so far away, and hidden behind such thick clouds of dust, that it’s hard to see. But big new telescopes, plus new techniques for sharpening the view through Earth’s atmosphere, allowed astronomers to track stars that are orbiting close to the galaxy’s heart. Precise tracking allowed them to plot the mass of the object the stars are orbiting — confirming the black hole’s existence.
UCLA astronomer Andrea Ghez leads one of the teams that confirmed it.
GHEZ: With the ability to beat the atmosphere, we could do this dynamics experiment and confine the mass to a much smaller volume. So you go from knowing there’s four million times the mass of the Sun confined in a region where you see lots of other stuff that could easily explain the mass that you’re seeing, down to a region that’s the size of our solar system. And at that point, there are no other alternatives to explaining this mass concentration and you really are left with a supermassive black hole. There’s still wiggle room, but theorists haven’t yet come up with an alternative, so the truth of the matter is this is the best case we have for a supermassive black hole anywhere in our universe.
But it’s a quiet black hole; we’ll talk about that tomorrow.
Script by Damond Benningfield, Copyright 2011
For more skywatching tips, astronomy news, and much more, read StarDate magazine.