Scientists using a gigantic radio telescope have captured the best view yet of two faraway galaxies colliding in deep space.

The Chile-based Atacama Large Millimeter/submillimeter Array (ALMA) and other telescopes employed a sort of cosmic magnifying glass to study a galaxy called H1429-0028, which lies about 6.9 billion light-years from Earth.

This phenomenon, known as gravitational lensing, occurs when a huge object in space such as a galaxy bends light coming from other bodies behind it. Lensing allows astronomers to peer at galaxies or other objects that would otherwise be too dim and distant to view. [Watch an animation of the galaxy merger]

"These chance alignments are quite rare and tend to be hard to identify," study lead author Hugo Messias, a researcher at both Conception University in Chile and the University of Lisbon in Portugal, said in a statement. "Recent studies have shown that by observing at far-infrared and millimeter wavelengths, we can find these cases much more efficiently."

The NASA/ESA Hubble Space Telescope and many other telescopes on the ground and in space have been used to obtain the best view yet of a collision that took place between two galaxies when the Universe was only half its current age.
The NASA/ESA Hubble Space Telescope and many other telescopes on the ground and in space have been used to obtain the best view yet of a collision that took place between two galaxies when the Universe was only half its current age.
Credit: NASA/ESA/ESO/W. M. Keck Observatory

In far-infrared light, H1429-0028 is one of the brightest gravitationally lensed objects available. It was first found in the Herschel Astrophysical Terahertz Large Area Survey, and is hard to see in visible light.

A suite of telescopes examined the galaxy, including ALMA, NASA's Hubble Space Telescope, the Keck Observatory in Hawaii and the Karl Jansky Very Large Array (VLA) in New Mexico. Hubble and Keck saw a ring of light around the foreground galaxy and also spotted large dust clouds within it, which made it tough to study the more distant H1429-0028. 

VLA and ALMA, however, are designed to peer through dust clouds. Their vision at longer wavelengths provided a clearer view of the background H1429-0028, revealing it to be two merging galaxies rather than a single object.

This diagram shows how the effect of gravitational lensing around a normal galaxy focuses the light coming from a very distant star-forming galaxy merger to created a distorted, but brighter view.
This diagram shows how the effect of gravitational lensing around a normal galaxy focuses the light coming from a very distant star-forming galaxy merger to created a distorted, but brighter view.
Credit: ESA/ESO/M. Kornmesser

The colliding galaxies seen in H1429-0028 are similar to those in the much closer Antennae Galaxies, astronomers said. But stars are being formed much faster in H1429-0028 — the equivalent of 400 suns per year compared with 20 or 30 suns per year in the Antennae system.

"With the combined power of Hubble and these other telescopes, we have been able to locate this very fortunate alignment, take advantage of the foreground galaxy's lensing effects and characterize the properties of this distant merger and the extreme starburst within it," said study co-author Rob Ivison, director for science at the European Southern Observatory. "It is very much a testament to the power of telescope teamwork."

The study was published Aug. 26 in the journal Astronomy & Astrophysics.

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