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Looking at the image below, you may think how cool the universe is to have a multi-core galaxy, but it’s an illusion. The universe is much cooler than that.

The Einstein Cross

It turns out that you aren’t seeing a galaxy at all, but most likely something behind it, like a quasar–the compact galactic cores that outshine nearly everything else in the universe.

A closer look at the Einstein Cross

But how could we be seeing something behind the galaxy that we are looking at? When the gravity of an object is intense enough, it can even bend light passing near it in a process called gravitational lensing. When the light rays bending around a massive object hit our eye, they don’t always synch back up into the single image that produced them. Instead, gravitational lensing can produce multiple image of the same object, which is perhaps my favorite effect in the cosmos.

Bending light around a massive object from a distant source. The orange arrows show the apparent position of the background source. The white arrows show the path of the light from the true position of the source.

While the physics behind gravitational lensing is complex, we more or less understand what is going on. In fact, Einstein himself used the phenomenon to corroborate his theory of general relativity.

When light misbehaves, it is always confusing. Having evolved brains that assume light moves in basically straight lines, we mistake the sky for pools of water in the desert and one galactic core becomes four.

Animated simulation of gravitational lensing caused by a Schwarzschild black hole going past a background galaxy.

And, as I like to think Bill Nye would say, if you don’t think that is some of the coolest s**t ever, get out of my face.

[Via Wikipedia, APOD]

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