This computer-simulated image shows gas from a tidally shredded star falling into a black hole. Some of the gas also is being ejected at high speeds into space. Credit: NASA, S. Gezari (JHU), and J. Guillochon (UC Santa Cruz)
Astronomers observed a flare in ultraviolet and optical light from the gas falling into the black hole and glowing helium from the star’s helium-rich gas expelled from the system.
The star resides in a galaxy 2.7 billion light-years away. The team’s results appear in online edition of the journal Nature.
“Black holes, like sharks, suffer from a popular misconception that they are perpetual killing machines,” said Ryan Chornock of the Harvard-Smithsonian Center for Astrophysics. “Actually, they’re quiet for most of their lives. Occasionally a star wanders too close, and that’s when a feeding frenzy begins.”
These images, taken with NASA’s Galaxy Evolution Explorer (GALEX) and the Pan-STARRS1 telescope in Hawaii, show a brightening inside a galaxy caused by a flare from its nucleus. The arrow in each image points to the galaxy. The flare is a signature of the galaxy’s central black hole shredding a star that wandered too close to it.
The top left image, taken by GALEX in 2009, shows the galaxy’s location before the flare. The galaxy is not visible in this ultraviolet-light exposure. In the top right image, taken by GALEX on June 23, 2010, the galaxy has become 350 times brighter in ultraviolet light.
The bottom left image, taken by Pan-STARRS1, shows the galaxy (the bright dot in the center) in 2009 before the flare’s appearance. The bottom right image, taken by Pan-STARRS1 from June to August 2010, shows the flare from the galaxy nucleus. Note how the light from the flare is much bluer (hotter) than the host galaxy light.