Astronomers have taken an extremely high-resolution image of a star in another galaxy, and it’s weird. 

The star in question is called WOH G64 (the 64^th giant star in a catalog compiled by astronomers Westerlund, Olander, and Hedin), and is located in the Large Magellanic Cloud, a small(ish) satellite galaxy of our own Milky Way. The exact distance is difficult to say, but it’s about 160,000 light-years from Earth.

That’s a long way. Far enough that seeing details near the star itself is incredibly difficult.

But astronomers are incredibly resourceful people. Here are those details:

OK, yeah, that’s really weird. So what are we seeing here?

Well first off, not the star. Let me explain…

WOH G64 is a red supergiant, a massive star well on its way to dying… and by dying I mean kaboom. Supernova. It was probably born with about 25 times the mass of the Sun, making it one of the elite few stars that massive. It raged through its life, fusing hydrogen into helium in its core, but eventually ran out of hydrogen. I’m not sure where it is in its evolution at the moment, but it may be fusing helium in its core, or even carbon. Eventually it’ll get to a point where the core is iron, and when it tries to fuse that, bad things happen. The core collapses and explodes, causing the outer layers to get torn away and flung off at a decent fraction of the speed of light, while the collapsed core most likely creates a black hole. So yeah, bad things.

But it’s not there just yet. At the moment the core is furiously radiating energy inside the star, which is absorbed by the star’s outer layers of gas, causing them to swell up enormously. The gas cools, glowing red, so it’s a red supergiant. It’s probably over 1,700 times the diameter of the Sun!

Seventeen hundred. If you replaced the Sun with WOH G64 in the center of our solar system, it would stretch nearly all the way to Saturn!

Oh, and did I mention that it’s blasting out nearly 300,000 times the energy the Sun does? I’m sorry I wasn’t sure if I forgot to mention that because thinking about it made my brain leap out of my skull and run around the floor screaming.

So yeah, the star is a bruiser. Here’s a key thing: Red supergiants like this are so bright the pressure from their starlight can blow off a wind of particles from their atmosphere. This is mostly hydrogen, but also has helium, carbon, silicon, and other stuff in it. The wind is dense in an astronomical sense, blowing out as much as several hundred times the mass of our entire planet in a year.

The carbon and silicates form tiny grains astronomers call dust, and this stuff is pretty opaque, blocking light behind it. Huge clouds of this material can enshroud red supergiants, so thick they sometimes completely block our view of the star. That’s why I said this image doesn’t show the star itself; WOH G64 is buried under septillions of tons of dust. 

In fact we knew it was cloaked in dust even before we had good images of the star; observations taken in different infrared colors show it was too red even for a red supergiant. The only explanation was hot dust ramping up the infrared luminosity.

It’s all that dust we’re seeing in this new image [link to journal paper]. Heated by the intense furnace below, that dust glows fiercely in the infrared, the wavelength these images were taken. The observations were made using the Very Large Telescope, which is actually four huge 8.2-meter telescopes. Using a complex method called interferometry, the light from the telescopes can be combined, acting together as if they were a single telescope 50 meters across, allowing them to see amazingly small details on distant objects. The entire image above is 15 milliarcseconds across — the full Moon in the sky is 120,000 times wider! So we’re seeing very tiny details, much smaller than even Hubble or JWST can see.

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