NGC 3783 is a spectacular face-on spiral galaxy about 125 million light-years from us. In its exact center is a supermassive black hole, some 30 million times heftier than our Sun (about 7 times more massive than Sgr A*, the central black hole in our Milky Way). It’s actively feeding, meaning material like gas is falling into it. As it does, this matter forms an accretion disk that gets very hot, and glows brightly.

These disks are made of ionized gas, material with electrons stripped away from their parent atoms. Moving charged particles make a magnetic field, so the NGC 3783 disk has a powerful field embedded in it. 

The magnetic field lines — the loops you can see when, for example, iron filings are spread around a bar magnet — store a vast amount of energy, and aren’t always stable. I like the analogy of a bag full of giant metal springs that have been bent and the ends very gently connected. If one snaps it sproings straight and releases its energy, slapping into other springs and triggering them too, generating a cascade you don’t want to stick your hand in. You get a huge burst of energy.

Same thing here. The magnetic field lines in the accretion disk can snap and release their energy, making a runaway effect, and it can be soul-chillingly powerful blast, outshining the entire galaxy at some wavelengths. In 2024 just such a flare was seen from NGC 3783, a blast of X-rays so powerful it was equal to 10 billion times the Sun’s luminosity [link to journal paper]!

But it did more than that: the data indicate that the explosion also sent out a huge blast of subatomic particles, what we call a wind, accelerated to immense speed. The wind velocity was measured to be a staggering 57,000 kilometers per second, or about one-fifth the speed of light! To get an idea of how much energy was involved in this, only about 10% of the energy went into the X-ray flare, the other 90% went into blasting out this material. So, 90 billion times the energy the Sun produces every second. 

Holy crap. Terrifying. I’m glad it’s far away.

I’ll note this happens locally too. If this all sounds familiar that’s because it’s very similar to a coronal mass ejection, a blast of material away from the Sun that happens when magnetic fields lines in the corona, our star’s outer atmosphere, snap. A billion tons of hydrogen can be launched away at terrific speed, and if it hits Earth it can cause all kinds of havoc here, from just beautiful aurorae to widespread black outs. In fact, the astronomers in their paper liken this accretion disk flare event to a CME and use the same equations to analyze it.

As I like to point out, we have a lot of reasons to study the Universe. Curiosity, exploration, the desire to understand, the beauty, the sheer wonder of it. Sometimes though it has practical benefits. The more we understand black holes, surprisingly, the more we can understand the Sun and its effects on Earth. That’s worth investigating, too.

Astronomers may have shown that a broiling exoplanet may have been able to retain an atmosphere, which is rather surprising. Of course, the air there may consist of red-hot vaporized rock…

The planet is called TOI-561 b. It’s a super-Earth, a rocky planet about 1.4 times Earth’s diameter, and it orbits an old star similar to the Sun. However, its orbit is extremely close to the star, so much so that it gets 4,000 times as much energy pounding it from the star as Earth does from the Sun! Its surface temperature should be something like 2,700° Celsius. That makes it a lava planet, its surface covered in molten rock.

It’s weird in another way, too: it seems to be much lower density than you’d expect for a rocky planet its size. One possibility is that it’s not as big as we think, and instead has a thick atmosphere which tricks us into assuming it’s bigger than it is.

A team of astronomers pointed JWST at it [link to journal paper]. The idea was to take observations across a complete orbital cycle of the planet (which is only 11 hours!) — as it orbits, it presents its dark side to us, then goes through phases like the Moon, going through first quarter, full, and so on. Note that we don’t actually see this as it’s too small and too far from us to see it! But as it goes through phases it gets brighter and dimmer, and that can be detected. The team also took spectra of the planet, by bring tricky: they took spectra when the planet was behind the star, so they only see the star itself, then again when the planet is visible. By subtracting off the star spectrum they are left with just the planet’s. This is very tricky to do, but they seem to have pulled it off.

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