Proof of the black hole is a tremendous amount of mass inside a very small volume. There's 4 million times the mass of our sun within a region that's comparable to the size of our solar system.
One of the big mysteries about the black hole at the center of the galaxy is, 'Why don't we see emission from matter falling onto the black hole, or, rather, the black hole eating up its surroundings?'
We have this interesting problem with black holes. What is a black hole? It is a region of space where you have mass that's confined to zero volume, which means that the density is infinitely large, which means we have no way of describing, really, what a black hole is!
There's a large cluster of stars that are orbiting the center of our galaxy. And by measuring the motion of stars, and in particular, their orbits, we can figure out whether or not there's a central black hole.
The key to proving that there's a black hole is showing that there's a tremendous amount of mass in a very small volume. And you can do that with the motions of stars. The way the star moves around the center of the galaxy is very much like the way the planets orbit the sun.
One of the key differences between galaxies with super massive black holes is whether or not the black holes are lit up, because they are basically bingeing on a lot of material in its surroundings.
I'm interested in finding whether or not there is a really massive, what we like to call 'super massive' black hole at the center of our galaxy. And the reason this is interesting is that it gives us an opportunity to prove whether or not these exotic objects really exist.
Astronomers are obsessed with building larger and larger telescopes. There are two promises that we make with bigger telescopes: that they can see fainter things and that they see more detail. But it's been really hard to follow through on that second promise because of atmospheric distortion.
The question that I started off with was, I thought, very simple. It was just 'Is there a massive black hole at the center of the Milky Way?' But one of the things I love about science is that you always end up with new questions.
The key to proving that there's a black hole is showing that there's a tremendous amount of mass in a very small volume. And you can do that with the motions of stars.
Black holes are very exotic objects. Technically, a black hole puts a huge amount of mass inside of zero volume. So our understanding of the center of black holes doesn't make sense, which is a big clue to physicists that we don't have our physics quite right.
How do you observe something you can't see? This is the basic question of somebody who's interested in finding and studying black holes. Because black holes are objects whose pull of gravity is so intense that nothing can escape it, not even light, so you can't see it directly.
Fortunately, most things around the supermassive black hole are just going to go around it. They're going to orbit it. They don't actually get sucked in.
Our galaxy's pretty ordinary, garden-variety. So if we believe our galaxy has a super massive black hole, that tells us that most, if not all, galaxies host such a black hole at their centers.
As an astronomer, I get to ignore the details of the things that we don't understand. There's a lot of work that we can do on scales that we do understand, and there is actually a finite size that I can associate with a super massive black hole.
The star S0-2 orbits around Sgr A* every 16 years and will go through its closest approach in 2018. That's an opportunity to test Einstein's General Relativity theory through very precise measurements of this star's short period orbit.
