Astronomers observe a galaxy pile-up unlike anything seen before

26 Apr 2018

Artist’s impression of the 14 galaxies detected by ALMA as they appear in the very early, very distant universe. Image: NRAO/AUI/NSF; S Dagnello

At the farthest edge of the known universe, astronomers were stunned to spot a cosmic pile-up of galaxies unlike anything seen before.

One day, it is envisioned that our Milky Way will collide with our neighbouring Andromeda Galaxy, creating a melded, single, giant galaxy – but not without a number of stars being violently ejected by the collision.

So, spare a thought for a recent discovery that shows an astounding number of galaxies – 14 in total – are about to become involved in a cosmic pile-up  at the farthest edge of the known universe.

Future Human

In a recently published paper, an international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) spotted the cosmic wonder – known as a protocluster – 12.4bn light years away, or the equivalent of 90pc of the way across the observable universe.

This means that its light started travelling to us when the universe was only 1.4bn years old, or about one-tenth of its present age.

Adding even more incredible numbers to the mix, each of the 14 galaxies is forming stars as much as 1,000 times faster than our own Milky Way, but are crammed into a region of space only three times the size of it.

As it continues, the pile-up is expected to form a colossal galaxy cluster, which will challenge our understanding of the birth of our universe.


Zooming in to the galaxies discovered by ALMA. The outer field is from data taken by the Herschel Space Observatory. The middle image – a portion of a much-wider survey by NSF’s South Pole Telescope – uncovered the distant galactic source that was studied by ALMA to reveal the 14 galaxies. Image: ALMA (ESO/NAOJ/NRAO), T Miller and S Chapman et al; Herschel; South Pole Telescope; (NRAO/AUI/NSF) B Saxton

Spectacular just to see

“Having caught a massive galaxy cluster in throes of formation is spectacular in and of itself,” said Scott Chapman, an astrophysicist at Dalhousie University in Halifax, Canada, who was involved in the research.

“But, the fact that this is happening so early in the history of the universe poses a formidable challenge to our present-day understanding of the way structures form in the universe.”

Existing theories and computer models have always predicted that protoclusters as massive as the one observed by ALMA should have taken much longer to evolve.

Co-author of the paper, Tim Miller of Yale University, commented: “How this assembly of galaxies got so big so fast is a bit of a mystery; it wasn’t built up gradually over billions of years, as astronomers might expect.

“This discovery provides an incredible opportunity to study how galaxy clusters and their massive galaxies came together in these extreme environments.”

Colm Gorey was a senior journalist with Silicon Republic