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Cosmic collision alters early universe thinking

ASTRONOMERS have detected the early stages of a colossal cosmic collision, observing a pile-up of 14 galaxies 90% across the observable universe in a discovery that upends assumptions about the early history of the cosmos.

Researchers said the galactic mega-merger observed 12.4 billion lightyears away from Earth occurred 1.4 billion years after the Big Bang that gave rise to the universe. Astronomers call the object a galactic protocluster, a precursor to the type of enormous galaxy clusters that are the largest-known objects in today’s universe.

It marked the first time scientists observed the birth of a galaxy cluster, with at least 14 galaxies crammed into an area only about four times the size of our averagesized Milky Way galaxy.

A protocluster as massive as this one, designated as SPT2349-56, should not have existed, according to notions of the early universe. Scientists figured this could not happen until billions of years later.

“We were staggered by the implications,” said astrophysicist Scott Chapman of Dalhousie University in Canada. “Conventional wisdom was that clusters take a lot longer to build up and assemble. SPT2349 shows us it happened more rapidly and explosively than simulations or theory suggested.”

The galaxies within SPT2349 were producing stars at a remarkable clip, up to a thousand times the Milky Way’s formation rate.

In observing objects so distant, astronomers are peering back in history because of the length of time light takes to travel. SPT2349-56 appeared when the universe was about a tenth its current age.

Researchers, who studied SPT2349 using land-based telescopes in Chile, said it most likely snowballed in size since 12.4 billion years ago and could be among the largest structures in the cosmos. – Reuters