A special space telescope has helped scientists gain a much better grasp on what's happening at the crowded center of our galaxy, according to findings published in Nature yesterday.
Earth is stuck near the edge of the Milky Way, tucked in a quiet spot just off of one of the galaxy's spiral arms. The center of our galaxy, on the other hand, is an extremely busy place. If we're in the suburbs, the galactic center is Times Square; it's packed full of stars that are dead or dying, giant gas clouds, and of course, one supermassive black hole. And while astronomers learn a lot about our galaxy by looking at its cosmic doppelgängers, there's still much to be gained by studying the busiest parts of our own.
If we're in the suburbs, the galactic center is Times Square
The problem is all that clutter makes studying the galactic center a difficult task. That makes it tricky to study high-energy x-rays and the special objects that emit them. But a paper published yesterday in Nature marks an important step in this process thanks to work done with the NuSTAR telescope by a group from Columbia University.
NuSTAR is the first space telescope that lets astronomers study high-energy x-rays in very fine detail, which makes it the perfect tool to cut through the low-energy clutter in the core of our galaxy. "It was like turning off the lights on all that low-energy stuff," says Kerstin Perez, a co-author of the paper who worked with the group at Columbia. With the noise out of the way, the astronomers found that the galactic center was also teeming with high-energy emissions.
But what are these emissions coming from? Perez says they're caused by one of two things: stellar remnants (white dwarfs, neutron stars, low-mass black holes) or cosmic rays emitted by the supermassive black hole. The leading theory thanks to these new observations is that it's likely the former, more specifically "accreting" white dwarfs — or as they're popularly referred to in astronomy, "vampire systems." The name comes from the way a white dwarf — which is the incredibly dense remnant of a once-burning star — sucks the matter off of a binary star companion, a common occurrence in the universe.
Vampire stars feed off their binary counterparts
The source of these emissions is still open to debate, and Perez says that each one of the possibilities creates its own complications. For example, if the high-energy x-rays are coming from dead stars, Perez says there's either something very different about the way they objects behave near the high activity of the galactic center, or we might have been wrong about how they behave in general.
Her questions unravel from there. "How did all those really heavy white dwarfs get there? Is it that they’re forming there? Or is it that they’re formed a little bit further away, and then through gravity they’re getting pulled in close to the galactic center? Or is it that, in combination with those two things, that there’s something about the really dense environment of the galactic center that these objects tend to become accreting objects with a much higher probability?"
Perez happily embraces all the new questions that her group's findings raise just as any good scientist would. She might not have those answers yet, but at least now the path is a little clearer.