The Hubble Telescope Finds a Light Warping 'Einstein Ring' in Distant Galaxy Cluster
In fact, the combined mass of these galaxies is so great that it causes something unusual to happen. When the Hubble Space Telescope snapped a photo of this distant cluster, the amount of mass space-time caused such a distortion in space-time that a bizarre circle appeared at the center of the cluster.
This is called gravitational lensing, also known as an "Einstein ring", and you can see a tiny photo of this giant cosmic phenomenon below:
#HubbleFriday These graceful arcs are examples of a phenomenon known as an Einstein ring. The light from a background galaxy is diverted and distorted around the massive intervening cluster, making it seem as though the galaxy is in several places at once: https://t.co/epW9RXHhM8 pic.twitter.com/TMRPW70YTg— Hubble (@NASAHubble) 6 April 2018
Gravitational lensing has its roots in general relativity, but the basic concept of what's happening is fairly simple to explain: when light passes by an extremely dense object with an immense gravitational pull, that object can actually disrupt the path the light is taking. What we see is light being forced to travel around the galaxy cluster because the cluster's distorted space-time prevents the light from moving in a straight line.
And when that happens, it can appear to outside observers (which would be you, in this case) that a galaxy is in several places at once, and the edge of the Einstein ring does resemble several stretched out copies of a single galaxy. That galaxy isn't actually in several places at once, of course, but it's distorting light enough that we can't see it normally.
We've seen gravitational lensing numerous times before, and this is actually one of the less imposing instances. Other Einstein rings can be much more intimidating, like the one we've found that vaguely resembles the Eye of Sauron from Lord of the Rings.
Thankfully, this looks more like a galactic optical illusion, rather than a god-like fantasy supervillain.