From Ethan Siegel: “A distant galaxy cluster and the power of Einstein’s gravity”

Starts with a bang
Starts with a Bang

1.11.16
Ethan Siegel

Temp 1
Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

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, [Albert] Einstein put forth a new theory of gravity: General Relativity. The solar eclipse of 1919 finally confirmed that mass gravitationally bent light around it.

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Images credit: New York Times, 10 November 1919 (L); Illustrated London News, 22 November 1919 (R).

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.


view the mp4 video here.

In 2014, the Hubble Space Telescope imaged an ultra-massive galaxy cluster found by the Sloan Digital Sky Survey3 [SDSS], and unveiled what appeared to be a spectacular, multiply-imaged distortion of blue, star-forming background galaxies.

NASA Hubble Telescope
NASA/ESA Hubble

SDSS Telescope
SDSS telescope at Apache Point, NM, USA

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Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

The multiple images of similar structures, the distortions and the similar colorations all pointed to gravitational lensing.

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Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

But a careful analysis of the data showed that while the outer arcs are indeed lensed background galaxies…

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Image credit: K. Sharon et al., 2014, via http://arxiv.org/abs/1407.2266.

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.

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Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

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.


view mp4 video here.

Despite our excellent intuition, there’s no substitute for good data.

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Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

See the full article here .

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“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan