Behold, the fattest thing in space

NASA has released a new image of two colliding galaxy clusters that are busy forming a single enormous entity nicknamed The Fat One by astronomers.

The entity – the name of which is more commonly rendered in Spanish, as El Gordo, and officially as ACT-CLJ0102-4915 – was first spotted in 2014 by the Hubble Space Telescope. {%recommended 5233%}

It was originally thought to be a single galaxy cluster, and comprises the mass equivalent of three million billion suns, making it the biggest and brightest X-ray cluster ever discovered.

Using data gathered earlier by ESO’s Very Large Telescope, NASA’s Chandra X-ray Observatory and the Atacama Cosmology Telescope, researchers subsequently found that El Gordo comprises two slightly less fat clusters in the process of merging into one. One study, published in The Astrophysics Journal, termed it “an unusually high-speed collision”.

The drama is the subject of intense research by astronomers around the world, not merely because of its inherent attractions, but also because it provides an exciting opportunity to observe the behaviour of dark matter and dark energy.

Astronomers suggest that much of El Gordo’s mass is hidden as dark matter, and that the rest of it comprises hot gas. As the collision continues, the gas and the dark matter are being torn away from each other. The gas is thought to be slowing down, while the dark matter moves at a constant velocity.