Well, recently as in about 25,000 years ago
Unprecedented variability of Sgr A* in NIR
Astronomers working out of the Keck Observatory in Hawaii have just announced that, in May of 2019, they observed the supermassive black hole at the center of our galaxy become 75 times brighter than it normally is. There's been a ton of speculation regarding what the heck caused the burst in infrared light, but it seems like a lot of astronomers, including those that discovered the flash, think that the supermassive black hole may be… feeding.
Before discussing the recent observation, which was reported in a paper titled Unprecedented Variability of Sgr A* NIR and comes via Vice, it should be noted that this event took place in the distant past — the very distant past. That's because the supermassive black hole being observed, dubbed Sagittarius A*, is a mind-bending 25,640 light years from Earth. Which means what we observed just a couple months back actually happened 25,640 years ago.
Now that that fact is out of the way, let's talk about the supermassive black hole exploding with brightness. In the tweet above, Tuan Do, one of the lead researchers who discovered the flash, notes that the video is a time-lapse of images taken over two-and-a-half hours (from the Keck telescope). Do notes that this observation was taken from an infrared portion of the electromagnetic spectrum that's just out of the band of visible light that people can see with their pedestrian peepers.
As the flash is unprecedented, astronomers admit that they don't actually know what caused it. But many of them, like Phil Plait,are guessing that the extraordinary increase in brightness was caused by either a subatomic particle "wind" that surrounds S2 (a star that orbits closely to the supermassive black hole), or perhaps G2, which is an unknown astronomical object that may be a dust cloud or a star surrounded by a dust cloud that also orbits near the black hole.
If this is the case, it's fair to say that this increase in brightness is due to the supermassive black hole "feeding" on some form of dust surrounding it. This is one reasonable hypothesis because as a black hole feeds on matter, it lights it up to enormous levels of brightness due to the matter's speed — the gargantuan mass of a supermassive black hole means that things that get near it increase in speed and turbulence (the matter bumps into each other) causing an increase in thermal radiation. And an increase in thermal radiation necessarily means an increase in electromagnetic radiation; in this case, infrared light. (We've all seen Predator, right?!)
Regardless of what caused the enormous flash of bright light from the supermassive black hole, one thing is certain: It's a lot of fun to guess about what happened. Oh, and we're also not in any danger from this event. That's important to note too, probably.
Unprecedented variability of Sgr A* in NIR
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