Black holes are flaring and stars are being kicked out of the galaxy at the American Astronomical Society conference

Posted by Sarah Scoles
on Thursday, January 09, 2014

The American Astronomical Society's (AAS) meeting is winding up, but the news continues apace as the conference's final hour approaches. Here are some reports from the field:

Help astronomers find the ages of star clusters in M83 using new data from the Hubble Space Telescope, released today at the American Astronomical Society meeting in Washington, D.C. // NASA/ESA/Hubble Heritage Team (STScI/AURA)
Big galaxies have big black holes (supermassive ones, in fact) at their centers. But Amy Reines and colleagues at the National Radio Astronomy Observatory discovered that tiny galaxies have tiny black holes. And here, “tiny” is relative, in that the black holes are known as “massive” rather than “supermassive.” Black holes of this size may help astronomers solve a mystery: How do much bigger black holes form? How does the universe make something millions of times as massive as the Sun? It's no small task (I'd like to see you try), and neither is figuring out their origins. 

In one particular dwarf galaxy, Peter Maksym of the University of Alabama saw an X-ray flare from a star being ripped apart by a massive (but not supermassive) black hole. 

This kind of interaction is what makes black holes (normally so black and hole-like) visible to astronomers. Closer to home, another such gravitational tug-of-war is happening near the Milky Way's central black hole. An object called G2, which is either a gas cloud or a star enshrouded within a gas cloud, is heading toward a romantic rendezvous with Sagittarius A*, the 4-million-solar-mass monster that holds our galaxy together. They will pass just 200 times the Earth-Sun distance from each other in March. Astronomers don't know exactly how much mass G2 has, so they don't know what kind of fireworks it's capable of generating, but, as presenter Leo Meyer of UCLA said is his team's motto, “The odds to see something are against you, but you have to look because if you see something, it will be spectacular.”

And people are looking. The Swift X-ray Telescope is monitoring the galactic center as part of an ongoing program. Similar to a squad car circling a neighborhood, their program will see suspicious characters that appear and then reappear, as well as one-off events. Already, they've turned up a magnetar, a bizarre kind of pulsar with an extreme magnetic field.

Hypervelocity stars are another kind of bizarre star discussed at the AAS meeting. These stellar NASCAR racers are traveling more than 1 million mph, fast enough to escape the cloying hold of Sagittarius A* and, thus, our galaxy. Lauren Paladino of Vanderbilt University in Nashville and her team went looking for Sun-like stars that were being similarly booted out. They found 20 such suns, but, curiously, the black hole didn't appear to be the one that had kicked them out. The team believes that these stars, traveling more than 1.5 million mph, encountered binary star systems that then slingshot them out of the galaxy. Hope they like eternal wandering and exile.

Participate in the discoveries: 

The Hubble Tarantula Treasury Project released an e-book with interactive features involving three of your senses. Smell, taste, and ESP! Just kidding: Touch, sight, and hearing. See what "sonification" means for a nebula.

Star Date: 83 is a citizen science project that will begin January 13. Help astronomers find the ages of star clusters in M83, using an extremely high-resolution image from the Hubble Space Telescope. Visit to learn more.

In case you missed our Google Hangout with Discover magazine yesterday, you can see the archived video of our chat about the latest exoplanet discoveries, alien cows, and the meaning of life.

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Exoplanets in the spotlight at the American Astronomical Society conference

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