Galaxies set to form enormous cluster

Galaxies clusters are the most massive structures in the known Universe, and astronomers have been given a perfect opportunity to study their formation.

An image of the galaxies captured by the Atacama Atacama Large Millimeter/submillimeter Array in northern Chile. Credit: ALMA (ESO/NAOJ/NRAO); B. Saxton (NRAO/AUI/NSF)

Astronomers are observing a pileup of 14 young galaxies that are set to merge into a massive galaxy cluster bound by dark matter.

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About 12.4 billion lightyears away, the protocluster – named SPT2349-56 – sits on the brink of becoming a one of the most massive structures in the known Universe.

The individual galaxies involved in the collision are forming stars about 1,000 times fast than the Milky Way, yet are crammed into a space just three times the size of our Galaxy.

These 14 galaxies are known as ‘starburst’ because they are producing new stars at an extraordinary rate.

Because the structure is so far away, its light began its journey to us when the Universe was about a tenth of its current age.

Galaxy clusters may contain as many as a thousand galaxies, and are thought to be held together by vast amounts of dark matter.

They also contain massive black holes and X-ray gas that can reach temperatures of over a million degrees Celsius.

An artist’s impression of 14 galaxies on the verge of forming the core of a massive galaxy cluster. Credit: NRAO/AUI/NSF; S. Dagnello
An artist’s impression of 14 galaxies on the verge of forming the core of a massive galaxy cluster.
Credit: NRAO/AUI/NSF; S. Dagnello

“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,” says Tim Miller of Yale University, co-author on the paper.

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

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The fact that the cluster is so far away and its components can be clearly identified offers an opportunity for astronomers to view the origins of cluster formation.