NASA telescope discovers black hole gulping star

A giant black hole displaying horrifying table manners has been caught in the act of guzzling a star in a galaxy 4 billion light-years away, scientists using an orbiting NASA telescope said on Tuesday.

Under the help of NASA's Galaxy Evolution Explorer, an orbiting telescope sensitive to two bands of ultraviolet wave lengths, astronomers for the first time saw the whole process of a black hole eating a star, from its first to nearly final bites.

Additional data from the Chandra X-ray Observatory, the Canada-France-Hawaii Telescope in Hawaii and the Keck Telescope, also in Hawaii, helped scientists chronicle the event in multiple wavelengths over two years.

"This type of event is very rare, so we are lucky to study the entire process from beginning to end," said Dr. Suvi Gezari of the California Institute of Technology, Pasadena, California.

Gezari is the leading author of a new paper appearing in the Dec. 10 issue of Astrophysical Journal Letters.

For perhaps thousands of years, the black hole rested quietly deep inside an unnamed elliptical galaxy. But then a star ventured a little too close to the sleeping black hole and was torn to shreds by the force of its gravity.

Part of the shredded star swirled around the black hole, then began to plunge into it, triggering a bright ultraviolet flare that the Galaxy Evolution Explorer was able to detect.

Today, the space-based telescope continues to periodically watch this ultraviolet light fade as the black hole finishes the remaining bits of its stellar meal. The observations will ultimately provide a better understanding of how black holes evolve with their host galaxies.

Black holes are heaps of concentrated matter whose gravity is so strong that even light cannot escape. Super massive black holes are believed to reside at the cores of every galaxy. Active black holes drag surrounding material into them, heating it up and causing it to glow. Dormant black holes, like the one in our Milky Way galaxy, hardly make a peep, so they are difficult to study.

That's why astronomers get excited when an unsuspecting star wanders too close to a dormant black hole, an event thought to happen about once every 10,000 years in a typical galaxy. A star will flatten and stretch apart when a nearby black hole's gravity overcomes its own self-gravity. Once a star has been disrupted, a portion of its gaseous body is then pulled into the black hole and heated up to temperatures that emit X-rays and ultraviolet light.

"The star just couldn't hold itself together," said Gezari, adding, "Now that we know we can observe these events with ultraviolet light, we've got a new tool for finding more."

The newfound feeding black hole is thought to be tens of millions of times as massive as our sun. Its host galaxy is located 4 billion light-years away in the Bootes constellation.

Source: Xinhua