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I’m travelling at the moment, so the newsletter is a bit shorter than usual this week and next week. It will be back to full length on the 19th!

An amazing Einstein ring

What’s better than an image of a beautiful galaxy? How about an image of two beautiful galaxies, where not only is one being gravitationally lensed by the other, but they are so perfectly aligned that the lensed image forms a complete ring? That’s called an Einstein ring, and this is the most mind bendingly perfect example I’ve ever seen. I thought I was looking at an AI-generated image at first.

The foreground galaxy is the fuzzy blob in the middle. It’s an elliptical galaxy – an older galaxy which has undergone so many mergers that it’s lost all of its spiral structure and is now just a featureless ball of stars. Wrapped around that is the slightly distorted image of a spiral galaxy which is in the background. The elliptical galaxy’s gravity has deflected the light from the spiral galaxy, focusing and magnifying it.

Gravitational lensing is one of those things that's useful for a ton of different things. It allows us to test our understanding of gravity, since the way the image has been lensed depends on the lens’ gravity. It allows us to study things in distant galaxies that we just wouldn’t be able to see if not for the magnification it provides. It allows us to measure the amount of dark matter surrounding distant galaxies and galaxy clusters (because of dark matter’s gravitational influence). The list goes on.

Sometimes, though, it’s not just about how useful something is. Useful or not, some things are just damn cool.

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Finally

I didn’t manage to see the UK’s recent partial solar eclipse, but luckily my Bluesky feed was full of photos and videos:

What is Three Alpha? Other than being the name of the newsletter you’re reading now, the name “three alpha” comes from the triple-alpha process, a nuclear chain reaction in stars which turns helium into carbon. Read more here.

Who writes this? My name is Dr. Adam McMaster. I’m an astronomer in the UK, where I mainly work on finding black holes. You can find me on BlueSky, @adammc.space.

Let me know what you think! You can send comments and feedback by hitting reply or by emailing [email protected].