Professional astronomers have access to the most powerful telescopes in the world, including Hubble and the Atacama Large Millimeter/submillimeter Array (ALMA). However, to see deep into the origins of the universe, sometimes they need to take a cue from Sherlock Holmes and rely on a magnifying glass: Thanks to the effects massive bodies like galaxies have on light, scientists were able to get enough of a boost to see the merging of two galaxies that took place when the universe was just half its current age.

Without the galaxy-sized “magnifying glass,” the event would have otherwise remained invisible.

“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,” explains lead author Hugo Messias of the Universidad de Concepción (Chile) and the Centro de Astronomía e Astrofísica da Universidade de Lisboa (Portugal). “Einstein predicted in his theory of general relativity that, given enough mass, light does not travel in a straight line but will be bent in a similar way to light refracted by a normal lens.”

The effect is called gravitational lensing, and it happens when the gravity of huge objects like galaxies and galaxy clusters bend light much the way a convex lens would here on Earth. The scientists say that the alignments between galaxies are rare, but are easier to find with far-infrared and millimeter wavelength technology.

Using composite images from several telescopes (including Hubble and ALMA), scientists were able to capture views of H-ATLAS J142935.3-002836, the brightest gravitationally lensed object to date. Images from Hubble and the Keck Observatory initially revealed that it’s an edge-on-disc galaxy, similar to our own. ALMA and the JVLA, able to see past the dust in such galaxies, revealed that H1429-0028 is actually a continuous collision between two galaxies (or, at least it was at the time the light emanating from it set out towards our telescopes, which was a very long time ago.).

They found that the ongoing collision produces hundreds of new stars each year.

“ALMA enabled us to solve this conundrum because it gives us information about the velocity of the gas in the galaxies, which makes it possible to disentangle the various components, revealing the classic signature of a galaxy merger. This beautiful study catches a galaxy merger red handed as it triggers an extreme starburst,” said Rob Ivison, ESO’s Director of Science.