ALMA Captures an Ancient Galaxy's Einstein Ring with Unprecedented Detail

ALMA has captured an image of a lensed galaxy that reveals a near-perfect Einstein ring. The new images are the highest resolution ever taken with the Atacama Large Millimeter/submillimeter Array (ALMA).

The ring itself was forged by the chance alignment of two distant galaxies. It's a rare and striking manifestation of gravitational lensing as predicted by Albert Einstein in his theory of general relativity.

Gravitational lensing occurs when a massive galaxy or cluster of galaxies bends the light emitted from a more distant galaxy, forming a highly magnified, though much distorted image. In this particular case, the galaxy known as SDP.81 and another galaxy line up perfect so that the light from the more distant one forms a nearly complete circle as seen from Earth.

"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," said Catherine Vlahakis, ALMA deputy program scientist, in a news release. "With the astounding level of detail in these new ALMA images, astroomers 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 information in the ALMA image may help astronomers to understand the bending of light done by the gravitational lens. By understanding this bending, the scientists can learn about the actual shape an internal motion of the distant galaxy.

"It takes a combination of ALMA's high resolution and high sensitivity to unlock these otherwise hidden details of the early universe," said Pierre Cox, ALMA director. "These results open a new frontier in astronomy and prove that ALMA can indeed deliver on its promise of transformational science."

The findings are published in the Astrophysical Journal Letters.

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