Astronomers say formerly active black hole is dormant in cosmic 'nap'

GREENBELT, Md., June 11 (UPI) -- U.S. astronomers say a black hole observed a decade ago consuming massive amounts of gas in the center of its galaxy has gone dormant, taking a cosmic "nap."

Two NASA space telescopes, NuSTAR and Chandra, observing the nearby Sculptor galaxy, have taken an X-ray look at the black hole and found it asleep, the space agency reported Tuesday.

"Our results imply that the black hole went dormant in the past 10 years," Bret Lehmer of Johns Hopkins University, Baltimore, and NASA's Goddard Space Flight Center in Greenbelt, Md., said.

"Periodic observations with both Chandra and NuSTAR should tell us unambiguously if the black hole wakes up again. If this happens in the next few years, we hope to be watching."

The slumbering black hole lies at the center of the Sculptor galaxy, also known as NGC 253, at 13 million light-years distance one of the closest star-forming formations to our own Milky Way galaxy.

"Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant," co-author Ann Hornschemeier of the Goddard center said. "NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it."

Almost all galaxies harbor supermassive black holes at their centers, thought to grow at the same rate that new stars form, until intense radiation from the black holes ultimately shuts down star formation.

In the case of the Sculptor galaxy, astronomers said they do not know if star formation is winding down or ramping up.

"Black hole growth and star formation often go hand-in-hand in distant galaxies," said Daniel Stern, a study co-author and NuSTAR project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It's a bit surprising as to what's going on here, but we've got two powerful complementary X-ray telescopes on the case."