Supermassive Black Hole

The center of our galaxy, the Milky Way, has a supermassive black hole. Of course no one has ever seen it. Nobody actually "sees" a black hole because it sucks up all the light near it. So how do we know that they exist at all? Well, if you use an infrared telescope to look at the center of our galaxy, you can see and plot the orbits of dozens of stars that are whizzing around some invisible center. The small tight orbits can mean only one thing.... a super massive gravitational object. Cool.