200 years in the past, the Milky Method’s central black gap briefly awoke

Someday between the American Revolution and the California gold rush, the black gap on the Milky Method’s coronary heart awakened.

The black gap, referred to as Sagittarius A*, has been quiet and dim because it was found within the Nineteen Nineties. It’s thought to have been largely quiescent for eons. However roughly 200 years in the past, the black gap, as seen from Earth, suddenly brightened as it let out a brief flare of X-rays, researchers report June 21 in Nature.

At about 26,000 light-years away, “Sagittarius A* is the closest supermassive black gap to us,” says astronomer Frédéric Marin of the College of Strasbourg in France. “Nevertheless it’s dormant.” If the black gap is accreting materials from its surrounding disk of fuel and dirt in any respect now, it’s at a low fee, making the behemoth troublesome to watch (SN: 5/12/22).

About 30 years in the past, astronomers detected brilliant X-rays from giant fuel clouds within the galactic middle. One clarification was that sooner or later, Sagittarius A* shot an X-ray pulse into house after consuming some cosmic materials, and the clouds recorded the afterglow (SN: 4/24/08). However different X-ray sources had been attainable.

Marin and colleagues used NASA’s Imaging X-ray Polarimetry Explorer satellite tv for pc to measure the polarization, or path, of the X-rays. “This path can act as a compass, pointing to the supply of emission,” Marin says. And it pointed straight on the black gap.

That polarization additionally means that the sunshine got here from a minimum of one X-ray pulse roughly 200 years in the past, the crew says. The X-ray fluorescence signifies that the black gap immediately grew 1,000,000 instances as brilliant as it’s now. It’s unknown how usually such pulses occur.

It’s additionally not clear what precisely brought on Sagittarius A* to flare. “It may very well be a large molecular cloud that was slowly accreted, or a really massive star that handed by and was accreted unexpectedly,” Marin says. “We don’t know but.”