In less time than it takes you to get ready for work, some X-ray emitting space objects become hundreds of times brighter than usual, then dim back down. But what those objects are, astronomers haven’t yet figured out.
In 2003 and 2007, scientists detected two superfast, super-bright X-ray flares near a galaxy called NGC 4697. No one had found anything like them before or since – until astronomer Jimmy Irwin at the University of Alabama in Tuscaloosa announced today that his team has caught two more such flares.
Irwin’s team originally planned to search through data from the Chandra X-ray Observatory to find star-sized black holes in groups of old stars around other galaxies. These black holes can up their X-ray emissions by a factor of five to 10 in around an hour as material swirls around the point of no return and gives off energy.
“But we found these extreme objects that varied by factors of 100 to 200,” says Irwin. “So it was a bit of an accident that we found the flares, as we were not originally looking for something so spectacular.”
In earlier X-ray observations of 70 galaxies, they found two such sources, around galaxies NGC 4636 and NGC 5128. The mystery objects both flared up in seconds and dimmed back to baseline X-ray brightness in about an hour. One erupted five times while telescopes happened to be watching, which means it probably acts up about every 1.8 days.
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