For the first time ever, astronomers have observed the birth of a galaxy cluster, known as a protocluster. The event, billions of light-years away, could form one of the largest-known structures in today’s universe.

Using the most powerful telescopes on Earth, the scientists have observed a group of 14 galaxies in the early stages of crashing into one another. The galaxies are forming stars at a rate 1,000 times faster than our own Milky Way galaxy. Yet all 14 galaxies fit into an area just about four times the size of our galaxy.

The gathering of galaxies is 12.4 billion light-years away from Earth. Because of the length of time it takes for light to travel, the scientists are actually looking back in history.

The protocluster, named SPT2349-56, appeared when the universe was about a tenth of its current age.

They say it happened 1.4 billion years after the Big Bang. The Big Bang is the explosive force that gave rise to the universe about 13.8 billion years ago.

Chris Hayward is a scientist with the Flatiron Institute in New York. He told the Simons Foundation, “This is the missing link in our understanding of how clusters form.”

The astronomers reported this galactic gathering in the journal Nature in late April.

History of the universe

Scott Chapman of Dalhousie University in Canada is one of the authors of the report. Chapman, Hayward, Tim Miller of Yale University and others observed the protocluster using the South Pole Telescope in Antarctica.

Chapman said how the group of galaxies got so big so fast "is a bit of a mystery.”

"It just hit you in the face because all of a sudden there are all these galaxies there," Chapman said. "We went from three to 14 in one fell swoop. It instantly became obvious this was a very interesting, massive structure forming and not just a flash in the pan.”

The protocluster was formed before the more mature galaxy clusters seen in the modern universe. That makes the protocluster an excellent test bed for learning more about how present-day clusters formed and evolved.

I’m Pete Musto.

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Words in This Story

cluster – n. a group of things or people that are close together

light-year(s) – n. a unit of distance equal to the distance that light travels in one year, about 9.46 trillion kilometers

galaxies – n. the very large groups of stars that make up the universe

journal – n. a magazine that reports on things of special interest to a particular group of people

author(s) – n. a person who has written something

in one fell swoop – idm. done all at once or all together

obvious – adj. easy to see or notice

flash in the pan – idm. a brief, intense effort that produces no really major result

mature – adj. grown to full size

evolve(d) – v. to change or develop slowly often into a better, more complex, or more advanced state