What’s the most reasonable thing to do after a heavy snack? Take a nap, of course! And that’s exactly what a certain black hole is doing. Almost ten years ago, NASA’s Chandra X-ray Observatory caught signs of the black hole snacking on gas at the middle of a nearby galaxy. Recently, however, NASA’s Nuclear SpectroscopicTelescope Array (NuSTAR), has taken a peek at the same black hole and has discovered that it is currently asleep.
The napping black hole is about 5 million times the mass of our sun and lies at the center of the Sculptor galaxy, a starburst galaxy that is actively giving birth to new stars. Being only 13 million light years away, this is one of the closest starbursts to our own Milky Way. Typically speaking, black holes usually only go dormant when they run out of material to feed on. However, this particular black hole is unusual because it seems to be napping in the middle of enormous amounts of star-forming activity going on all around it. In other words, there’s plenty of food around, but the black hole has, apparently, had its fill.
“Black hole growth and star formation often go hand-in-hand in distant galaxies,” said Daniel Stern, a NuSTAR project scientist. “It’s a bit surprising as to what’s going on here.”
This discovery will help teach astronomers how galaxies grow over a period of time. All galaxies are suspected of having black holes. In the most massive of these, those black holes are thought to grow at the same rate that new stars form until the radiation from the black hole shuts down star creation. At the present, astronomers are unaware if the Sculptor Galaxy’s star formation is increasing or decreasing.
Bret Lehmer of the Johns Hopkins University in Baltimore and NASA’s Goddard Space Flight Center in Greenbelt said, “Our results imply that the black hole went dormant in the past 10 years. 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.”
For now, though, we’ll just have to let sleeping black holes snooze.