Mostly Mute Monday: A distant galaxy cluster and the power of Einstein’s gravity
![](https://preprod.bigthink.com/wp-content/uploads/2016/01/1-UPtIsRLiyl_6MRgWfOgcQ.jpeg?w=480&h=270&crop=1)
The ability for mass to bend and magnify background light is a unique feature of General Relativity. But it can fool us, too.
“Gravitational and electromagnetic interactions are long-range interactions, meaning they act on objects no matter how far they are separated from each other.” –Francois Englert
A century ago, Einstein put forth a new theory of gravity: General Relativity. The solar eclipse of 1919 finally confirmed that mass gravitationally bent light around it.
![](https://cdn-images-1.medium.com/max/800/0*4-CLojyvN8IdIzW2.png)
But only much later was the phenomenon of gravitational lensing confirmed: where a distant galaxy cluster acted as a lens, magnifying and distorting the background galaxies behind it.
In 2014, the Hubble Space Telescope imaged an ultra-massive galaxy cluster found by the Sloan Digital Sky Survey, and unveiled what appeared to be a spectacular, multiply-imaged distortion of blue, star-forming background galaxies.
![](https://cdn-images-1.medium.com/max/800/0*Ct5-2ekRmW9ZC7FU.jpg)
The multiple images of similar structures, the distortions and the similar colorations all pointed to gravitational lensing.
![](https://cdn-images-1.medium.com/max/800/0*aRJf5HKm3e-pXhM0.jpg)
But a careful analysis of the data showed that while the outer arcs are indeed lensed background galaxies…
![](https://cdn-images-1.medium.com/max/800/0*OF4xhG_ADTEzjVSi.jpg)
the brightest blue lights, interconnecting the two giant ellipticals at the cluster’s center, come from the merger of the galaxies and the surrounding gas themselves.
![](https://cdn-images-1.medium.com/max/800/0*ghwuH9ywByA2BkPU.jpg)
What we’re looking at is a combination of the stars and galaxies of the foregrounds cluster, some 4,000 times as massive as the Milky Way, a transient burst of star formation, and only a few background objects.
Despite our excellent intuition, there’s no substitute for good data.
![](https://cdn-images-1.medium.com/max/800/0*BblnxDjU9aXclOTB.jpg)
Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images, video and no more than 200 words.
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