Sgr A* is the supermassive black hole in the center of our galaxy, the Milky Way. It has a mass 4 million times that of the Sun, and is considered quiescent, meaning it’s not actively eating copious amounts of matter and blasting out high-energy light (remember, the black hole is black, but the stuff around it can get quite hot as it falls in — that’s what’s shown in the famous images released a few years ago, seen above). Evidence has been piling up, though, that a few centuries ago Sgr A* had a decently massive outburst of X-rays.

New observations strongly support that idea. Astronomers used a new JAXA X-ray observatory called XRISM to observe a cold molecular cloud near Sgr A* in the galactic center [link to journal paper]. Called G0.11-0.11, it’s a giant dense cloud of cold gas likely around 100 light-years from the black hole, so pretty close on galactic terms. The weird thing is, we see X-rays from it. That would be surprising from something so cold, but it can actually fluoresce; that is, if hit by X-rays, the iron atoms in it get excited and re-emit X-rays in response (kinda like a glow-in-the-dark toy, just on a vastly larger scale and with scarier high energies). 

There are two ways this can happen. One is if the black hole flared; a big blob of matter fell into it, formed a disk around it, got super hot, and emitted X-rays that then hit the cloud and caused it to fluoresce. The other way is for the cloud to get hit by cosmic rays, which are super-fast subatomic particles zipping around in space. Those can also excite the gas, causing it to emit X-rays.

XRISM can be used to tell these two methods apart. Cosmic rays hitting the gas will create secondary effects, basically more emission from iron at different energies. A flare won’t do that. These secondary iron emissions are faint and couldn’t be detected by earlier X-ray telescopes, but XRISM should be able to see them… but in these new observations, it didn’t. This strongly supports the idea that the culprit was Sgr A*. 

Since this emission acts like an echo, and we can estimate the distance from the black hole to the cloud, it’s possible to calculate when the flare occurred. The authors get an answer of a few centuries, which aligns with previous work from other astronomers looking at evidence for a past flare. If so, they find the energy in the flare was 10³⁸ ergs, or the same amount of energy the Sun emits in about 7 hours. It’s unclear how long the flare lasted, but that’s still a decent amount of energy, and that’s just in X-rays alone. Adding up all the light from across the electromagnetic spectrum it was likely a lot more energetic even than that.

There’s another idea that Sgr A* flared twice, once about 230 years ago and a second time 130 years ago. If true, then the cloud may light up in X-rays again in a few decades. If that happens, then we’ll know for sure what’s to blame. Also, there are other clouds nearby, so hopefully future observations will see them light up in X-rays as well, which will really pin down the physics of what happened.

Of course, I have to add that there’s no reason to panic here. Some black holes put out immense amounts of radiation, but ours is more of a pipsqueak, and there’s a lot of dust and gas between us and it able to absorb a lot of the blow. Also, it’s 260 quadrillion kilometers away, so we’re pretty safe. 

In BAN Issue 957 I wrote about a binary star called TOI-2267, where each star likely has a planet orbiting it, saying this was the first kind of system like it found. However, exoplanet researcher Andrea Bernagozzi pointed out that’s not correct: another had been found in 2014, called XO-2 (or more officially BD+50 1471). What I should have said is that TOI-2267 is the first compact binary system like that found, where the stars are quite close together (making planetary formation more dicey), and that the planet orbits are seen edge-on from Earth, so we can study them via the transit method, where the planets pass directly in front of their host stars and we get mini-eclipses. That may sound a bit esoteric but the difference is important both in how we study these objects and how they form, so my mistake was actually enough to be worth correcting and updating y’all here. My apologies!

On Bluesky recently a colleague of mine posted a funny if aggravating shot of a workflow someone generated using AI, and of course it’s full of hallucinated BS, with made up words like “continvoucly morged”.

This immediately made me think of what I consider to be one of the funniest videos ever made: “The Turbo Encabulator”.

I cannot watch that without laughing. It’s so perfect, and the delivery is just astonishing. There have been other versions of it, but this is the original and the best.

The text of the video is actually from an essay published in 1944! Wikipedia has a good history of it.

I remember when I was a kid, my dad —  an engineer himself — gave me a copy of the text he found somewhere. I was in high school, I think, and laughed myself silly reading it. The writing aligns almost perfectly with my sense of humor, and it influenced me for years. Probably still does. My wife (who is not an engineer and is science-adjacent) also loved it, and still sometimes drops a mention of the reciprocating dingle arm into conversation. She knows how to sweet-talk me.

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