Washington: Nearly 10 years ago, NASA`s Chandra X-ray Observatory caught signs of what appeared to be a black hole snacking on gas at the middle of the nearby Sculptor galaxy.
Now, NASA`s Nuclear Spectroscopic Telescope Array (NuSTAR), which sees higher-energy X-ray light, has taken a peek and found the black hole asleep.
"Our results imply that the black hole went dormant in the past 10 years," said Bret Lehmer of the Johns Hopkins University, Baltimore, and NASA`s Goddard Space Flight Center, Greenbelt, Md.
"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," added Lehmer, lead author of a new study detailing the findings.
The slumbering black hole is about 5 million times the mass of our Sun. It lies at the center of the Sculptor galaxy, also known as NGC 253, a so-called starburst galaxy actively giving birth to new stars. At 13 million light-years away, this is one of the closest starbursts to our own galaxy, the Milky Way.
The Milky Way is all around more quiet than the Sculptor galaxy. It makes far fewer new stars, and its behemoth black hole, about 4 million times the mass of our Sun, is also snoozing.
"Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant," said co-author Ann Hornschemeier of Goddard.
"NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it," Hornschemeier added.
The findings are teaching astronomers how galaxies grow over time
If and when the Sculptor`s slumbering giant does wake up in the next few years amidst all the commotion, NuSTAR and Chandra will monitor the situation. The team plans to check back on the system periodically.
A paper detailing the findings is to appear in the Astrophysical Journal.