ALMA Spots Einstein Ring (It's Not Eye Of Sauron) In Amazing Image Of Distant Lensed Galaxy


Astronomers have released an image of a cosmic phenomenon known as an Einstein Ring — so-named because Einstein's theory of general relativity predicted such things — and because it is the finest example seen so far.

Such a ring is the result of a massive galaxy bending the light of a smaller, less visible one behind it to bring it into visible form; the ring is formed because the light of the two galaxies lines up perfectly to form a circle.

The effect is the result of gravitational lensing, and while such sights are fairly common, the result is usually a partial arc or a distorted filament of light; true, circular Einstein Rings are rare.

Astronomers began finding Einstein Rings in the late 1980s, although most were only partial rings because of slightly off-center alignments of the galaxies involved.

That's what makes the new image — a perfect example of the phenomenon — so dramatic, they say.

The image of the distant, now-made-visible galaxy known as SDP.81 was captured by the world's most powerful ground-based observatory, the Atacama Large Millimeter/submillimeter Array (ALMA) in the Atacama Desert in Chile.

"Though this intriguing interplay of gravity and light in SDP.81 has been studied previously by other observatories ... and visible light observations with the Hubble Space Telescope, none has captured the remarkable details of the ring structure revealed by ALMA," the National Radio Astronomy Observatory, which operates the ALMA instrument, said in a statement.

It is almost 12 billion light years away, while the close galaxy acting as the "lens" is just 4 billion light years distant.

That means we're seeing SDP.81 was it existed when the universe was just 15 percent of its current age, the astronomers note.

"Gravitational lensing is used in astronomy to study the very distant, very early universe because it gives even our best telescopes an impressive boost in power," says Catherine Vlahakis, ALMA Deputy Program Scientist. "With the astounding level of detail in these new ALMA images, astronomers will now be able to reassemble the information contained in the distorted image we see as a ring and produce a reconstruction of the true image of the distant galaxy."

The new SDP.81 images were captured as part of ALMA's Long Baseline Campaign, a test of the telescope's highest resolving power created when its antennae are at their greatest separation of almost nine miles apart.

The resolution achieved is comparable to being able to see the rim of a basketball hoop mounted on the Eiffel Tower in Paris from the observation deck of the Empire State Building in New York, the NRAO says.

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