Behold Hubble’s Cosmic Snake!

Warped by the gravity of a foreground galaxy cluster, this much more remote galaxy has been stretched into a cosmic snake. ESA/Hubble, NASA

If you can’t wrap your head around every aspect of Einstein’s Theory of Relativity, that’s understandable. Neither can I. But when it comes to massive objects warping the fabric of space — one of its more dramatic predictions — the Hubble Space Telescope help us make sense of this bizarre phenomenon.

Can you spot the Snake? This image from Hubble shows a wider, more complete view of the galaxy cluster MACSJ1206.2-0847. Galaxy clusters like these have enormous mass, and their gravity is powerful enough to visibly bend the path of light, somewhat like a magnifying glass.  Located 4.5 billion light years from Earth, the cluster contains about a quadrillion (1,000,000,000,000,000) times the mass of our sun. NASA, ESA, M. Postman (STScI) and the CLASH Team

Hubble recently captured a photo of the Cosmic Snake, a distant galaxy peppered with clumpy regions of intense star formation (blue dots and dashes along its length) warped by the effect of gravitational lensing. Although it appears to be slithering between normal-looking galaxies, the giant object is actually far behind a foreground galaxy cluster called MACSJ1206.2-0847 in the constellation Corvus.

The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of a distant galaxy (upper left) behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Einstein predicted that massive objects would bend the fabric of space-time (the dimple shown here below the cluster). Light follows the curve of the dimple, coming to a focus to reveal the remote galaxy from our perspective on Earth.  NASA, ESA, L. Calcada

Light from the distant galaxy arrives at Earth after passing through the powerful gravitational field of the intervening cluster. Picture the field as a giant lens that focuses and brightens the light of distant objects in the background into images, similar to what an optical telescope does except with added distortion.


Want to get an inkling of what space-time’s all about? The short (5-minute) lesson and graphics in this video will help.

Of course, this metaphor only goes so far. In reality, there’s no lens at all, only light coming to a focus after following the contour of the bowl-like depressions made by the cluster in the 4-dimensional fabric of space-time. Instead of traveling in a straight line, the way we usually think about light’s direction, it weaves and bends according to the local fabric of space-time.

The barred spiral galaxy NGC 253 is 11.5 million light-years from Earth and the brightest member of the Sculptor group of galaxies. Like the Cosmic Snake, it’s also undergoing intense star formation. Just look at all the fresh, blue stars that light up the disk. Were it not for lensing distortion, the Snake might look something like this distortion-free, more local galaxy. Paul Luckas, ICRAR

Here’s the killer thing. Were the cluster not there, we probably wouldn’t even see the Snake, but thanks to lensing, it’s not only plainly visible but smeared into a whimsical shape. Sometimes gravitational lensing can even produce multiple images of the object as light is bent in different directions around the foreground cluster. Using Hubble, astronomers recently looked at five such images of the Cosmic Snake, each with a different level of magnification. Using this technique, the galaxy and its features could be studied on different scales. The highest-resolution images revealed that giant clumps in remote galaxies are made up of a complex collection of smaller clumps, which contributes to our understanding of star formation in distant galaxies.

 

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