Collision of distant galaxies revealed through galactic lens

From the far reaches of space, astronomers brought two colliding galaxies into sharp focus by patching together images from several powerful telescopes. That, and the luck of a rare "galactic lens."

"While astronomers are often limited by the power of their telescopes, in some cases our ability to see detail is hugely boosted by natural lenses created by the Universe," the lead researcher, Hugo Messias, explained in a press release.

A giant, heavy object bends light from objects behind it due to its strong gravity - an effect called gravitational lensing. Astronomers can study objects through such a cosmic magnifying glass that would otherwise be invisible. But for a gravitational lens to work, the foreground lensing object - in this case a galaxy - and the one beyond it need to be precisely aligned.

That's what happened in this rare instance.

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Using gravitational lensing, ALMA, the VLA, and many other telescopes obtained the best view yet of a collision that took place between two galaxies when the Universe was only half its current age. The foreground galaxy is doing the lensing and around it is an almost complete ring -- the smeared out image of a star-forming galaxy merger far beyond. This picture combines the views from the Hubble Space Telescope and the Keck-II telescope on Hawaii (using adaptive optics).
ESO/NASA/ESA/W.M. Keck Observatory

"These chance alignments are quite rare and tend to be hard to identify," said Messias, of the Universidad de Concepción in Chile and the Universidade de Lisboa in Portugal. But by combining the images of telescopes that use different wavelengths of light "we can find these cases much more efficiently."

The colliding galaxies, officially designated HATLAS J142935.3-002836 (or H1429-0028 for short) are among the brightest gravitationally lensed objects ever observed, the researchers say.

Astronomers were able to generate even more detailed images by combining observations from the Hubble Space Telescope, Atacama Large Millimeter/submillimeter Array (ALMA), the Karl G. Jansky Very Large Array (VLA), the Keck Observatory, and other telescopes.

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The foreground galaxy is doing the lensing and around it is an almost complete ring -- the smeared out image of a star-forming galaxy merger far beyond. This picture combines the views from the Hubble Space Telescope and the Keck-II telescope on Hawaii (using adaptive optics) along with the ALMA images shown in red. The ALMA data also give information about the motions of the material in the distant merging galaxies and were vital in unravelling the complex object.
ESO, ALMA (NRAO/ESO/NAOJ); W.M. Keck Observatory; NASA/ESA

The astronomers released videos illustrating their findings (seen above). First the viewer zooms through space to locate the colliding and merging galaxies, and then we see how gravitational lensing magnifies and brightens distant objects.

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