The supermassive black hole in the center of our galaxy has started to stir and astronomers are pondering whether the uptick in flare activity has been triggered by the passage of a mysterious dust-enshrouded star.
PHOTOS: Chandra's X-Ray Supernova Remnant Stunners
Until recently, the Milky Way's supermassive black hole - that resides in a region of our galaxy's core called Sagittarius A* - has been generating bright flares roughly once every 10 days. Over the past year, however, activity has increased and Sagittarius A* (or Sgr. A* for short) has been flaring roughly once per day.
Using data from 3 space telescopes, astronomers have been able to better understand these powerful flaring events and they may have found a fascinating cosmic connection.
"For several years, we've been tracking the X-ray emission from Sgr A*. This includes also the close passage of this dusty object," said Gabriele Ponti, of the Max Planck Institute for Extraterrestrial Physics in Germany, in a Chandra press release. "A year or so ago, we thought it had absolutely no effect on Sgr A*, but our new data raise the possibility that that might not be the case."
ANALYSIS: Our Galaxy's Black Hole Does NOT Have the ‘Munchies'
NASA's Chandra X-ray Observatory and ESA's XMM-Newton, with complementary data from NASA's Swift satellite, were used to piece together Sgr. A*'s activity as a dusty cloud approached the black hole. Discovered in 2011, astronomers were excited by the prospect of an object, called simply "G2″, would encounter Sgr. A*, and possibly be consumed after getting caught in the black hole's gravitational well. Had this happened, astronomers hoped to see a massive flare, giving humanity a wonderful glimpse into the high-energy processes erupting in a black hole's accretion disk and event horizon.
Alas, as G2 made close approach in 2014... nothing happened. At least, nothing obvious happened.
Before close approach, it was thought that G2 was most likely a cloud of dust and gas; possible stellar remnants idly orbiting through the galaxy's core. But after its supermassive encounter, G2 continued on its merry way, zooming around the black hole and orbiting back out into interstellar space. That's when G2′s nature became clear - it was probably a star, cocooned in a dusty envelope, whose gravity maintained its form and little of the cloud's material was allowed to be ripped away and fall into the black hole.
ANALYSIS: Why Our Galaxy's Black Hole Didn't Eat Mystery Object
Although our supermassive black hole had the munchies, its G2 snack was ripped from its clutches.
No doubt extreme gravitational perturbations disrupted the star and associated cloud, but there was no evidence of any flaring activity, meaning G2 had escaped pretty much intact.
In new research accepted for publication in the journal Monthly Notices of the Royal Astronomical Society, however, it seems that Sgr. A* has been the site of an uptick in flaring activity, a possible sign that some of the dust from G2 did indeed get pulled into the black hole, generating near-daily blasts of X-ray radiation.
"There isn't universal agreement on what G2 is," said Mark Morris of the University of California at Los Angeles. "However, the fact that Sgr A* became more active not long after G2 passed by suggests that the matter coming off of G2 might have caused an increase in the black hole's feeding rate."
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Of course, correlation doesn't necessarily mean causation; there may be another explanation for the increase in flaring activity - if this increase is real at all.
It could be that stellar winds near the black hole have been feeding Sgr. A* with more material, causing an increase in activity. Or it could be that we have gotten better at detecting these X-ray flares and the daily flaring activity has only just been discovered in the data. But the possibility that G2 might be to blame is exciting as we could be getting one of the first looks into the cause and effect of an object messing with the feeding habits of a black hole.
"It's too soon to say for sure, but we will be keeping X-ray eyes on Sgr A* in the coming months," said co-author Barbara De Marco, also of Max Planck. "Hopefully, new observations will tell us whether G2 is responsible for the changed behavior or if the new flaring is just part of how the black hole behaves."