Yes, The Cheshire Cat Cluster Is A Real Thing
We love to hear from our Curiosity Box subscribers, and one thing a few members have told us is that people who see them wearing this shirt think it’s just a fun, astronomy-inspired design that we made up. The truth is much, much more amazing: the Cheshire Cat Cluster is a real astronomical phenomenon, it actually looks like that, and it showcases two incredible topics in science: galactic collisions and gravitational lensing. And it’s one of the few fashion statements you can wear that shows proof that Einstein was right!
First of all, what you’re looking at: the Cheshire Cat Cluster is a galaxy cluster roughly 4.6 billion light years away (some of the galaxies are closer than others, of course). That’s so far away that the image on your shirt is about 1.45 million light years across. Since the Milky Way is just 103,000 light years across, so you could fit over 13 Milky Ways in that shot. The picture on your tee is actually a combination of two images taken in different wavelengths of the electromagnetic spectrum: the white shows “normal” visible light taken by the Hubble Space Telescope; the purple is data from the Chandra X-Ray Observatory. We combined the two into a hybrid image to make the phenomenon even clearer and lend some color to the shirt.
The two “eyes” are gigantic galaxies that are engaged in a massive collision with each other, happening at over 300,000 miles per hour (482,803 KPH). The giant purple coloration is gas that has been heated to several million degrees, providing evidence that the galaxy groups are slamming into one another. A 2015 study shows that sometime in the next billion years, the two galaxies should finish combining, forming one gigantic galaxy (if you want to read it, you can, here). Oh, and bonus fact: X-ray emissions also tell us that the center of the left eye is an actively feeding supermassive black hole.
And that’s not even the coolest part! The arcs that form the “face” are actually the images of four galaxies behind the cluster that are being stretched and bent by a tremendous amount of mass that distorts them into that shape, creating what is called an Einstein or Chwolson Ring. The process is known as gravitational lensing, and it is the observable effect of a prediction made by Einstein’s General Theory of Relativity: that a sufficient amount of mass can bend even light.
In fact, it was an observation of gravitational lensing in 1919 taken during a solar eclipse that first confirmed Einstein’s theory. Interestingly, this both made Einstein a household name around the world, and possibly saved the life of the astronomer who made the discovery, Arthur Eddington. Eddington was set to be drafted to fight in the trenches of WWI, but he was a pacifist Quaker. He had the option to be sent to the war or to prison, but the sentence was put on hold for him to conduct his experiments; and by the time the eclipse occurred, the war was over!
For the Cheshire Cat Cluster, what’s causing this lensing effect is the mysterious “dark matter,” which we know exists because we can see it’s effects (like lensing!), but haven’t been able to detect with observations along the electromagnetic spectrum. That’s actually one of the few things we do know about dark matter–even NASA says “we are much more certain what dark matter is not than we are what it is.” We know it’s not regular matter like the stuff that makes up humans, galaxies, and ice cream. It’s possibly exotic particles like axions or Weakly Interactive Massive Particles (WIMPs). Right now, all we know is it makes for a really, really cool shirt.
We hope you enjoy your relativistic fashion. Wear it for Einstein!