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?'
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 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.
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.
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.