Andrea Ghez is an astronomer and a specialist in black holes. She begins her talk today by asking: How do you observe something you can’t see? It’s a basic question for someone studying black holes. Then, she asks an even more intriguing question: Is there a supermassive one at the center of our gravity?
Ghez clarifies that ordinary black holes are the end state of a star’s life. Supermassive black holes are thought to reside at the center of galaxies, and of course, galaxies come in all shapes and sizes. There are some galaxies, she calls them the primadonnas of the galaxy world, that are very active. These galaxies appear to have jets emanating out from their centers. Some think this is evidence of supermassive black holes on to which matter is falling. And some think, Ghez included, that maybe all galaxies have these at their centers.
If we’re going to look for black holes at the center of galaxies, Ghez says the best place to look is in our own galaxy — the Milky Way. It makes sense as the next closest is 100 times further away. Her team uses the stars’ orbits of the black holes to measure their radii. To see these star orbits they use the largest telescope in the world, Keck I, based in Hawaii. Even with the largest telescope in the world, Ghez explains that they have to employ the technology of adaptive optics to correct for fluctuations in the atmosphere and have a clear view of the stars. Otherwise, she jokes, it’s like looking at a pebble at the bottom of a stream.
At this phase, Ghez and her team have begun testing their ideas. The team expected old stars to be clustered around these black holes, but young stars to be far away, as the black holes should pull their delicate new energy formations apart. Surprisingly, they found the exact opposite to be true. How are they resolving this contradiction? Ghez says her grad students are at the telescope in Hawaii as we speak.