I like my black holes like I like my internal organs: doing what they’re supposed to and not surprising anyone. After all, we barely even understand black holes beyond descriptions that would fit perfectly in an H.P. Lovecraft novel—a dead star at the center of the galaxy, collapsed under its own tremendous mass to an impossible singularity, warping the very fabric of reality around it like a cloak blacker than the blackest night, as even light itself struggles feebly and fails to escape its terrible pull. Yeah, I don’t want any surprises from black holes.
But alas, the great old one has awakened and all humanity’s brightest minds know not for what weird purpose. According to astronomers, the supermassive black hole at the center of the Milky Way has been acting really strange. Sagittarius A* (Sgr A*) is a pretty quiet and mundane supermassive black hole (as far as they go). It’s fluctuations in the brightness of the “electromagnetic counterpart” are normally relatively small. This summer, however, that seems to have changed. Observations from the Keck telescope have recorded massive spikes in the brightness of Sgr A*, including one when the black hole spiked to 75 times its normal brightness and held there for a period of two hours.
Astronomer Tuan Do at the University of California Los Angeles, who observed the unprecedented spike in Sgr A* says:
“I was pretty surprised at first and then very excited. The black hole was so bright I at first mistook it for the star S0-2, because I had never seen Sgr A* that bright. Over the next few frames, though, it was clear the source was variable and had to be the black hole. I knew almost right away there was probably something interesting going on wit h the black hole.”
Tuan Do’s research was recently published in the Journal of Astrophysical Letters, but astronomers still don’t know what’s caused these massive spikes. Black holes don’t emit light on their own (go figure), but the swirling disk of stuff around it does. The so-called accretion disk consists of dust and gas and busted up cosmic debris that is pulled towards the black hole but doesn’t make it past the event horizon. Sometimes unlucky stars passing through the neighborhood have their matter ripped out by the supermassive black hole’s enormous gravity and assimilated by the accretion disk. The working hypothesis for the spikes in Sgr A*’s brightness is that it got its claws on an unusually large object and pulled it into the accretion disk, though what the object could be is unknown.
Astronomers will keep studying Sgr A* and try to figure out just what it’s up to. The Keck telescope only has a few more weeks where it will have the right angle to observe Sgr A*, but there are four more telescopes that have been pointed at it all summer with their data yet to be released. After that, the center of our galaxy won’t be observable again until 2020. Which leaves an approximately six month blind spot, and as everyone knows, black holes only strike when you’re not looking.
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