Astronomers Discover Oldest Galaxy Protocluster Yet

Twelve galaxies within an enormous protocluster 200 million light-years wide were discovered by an international team of astronomers, who said in a study that the star formations are the oldest observed to date and shed light on cluster formation early in the life of our universe. (NAOJ / Harikane)

(CN) – An international team of astronomers wielding the observational power of three massive telescopes have discovered a 13 billion-year-old galaxy cluster, the oldest grouping of star systems observed to date in the cosmos, according to a study released Thursday.

In the known universe, galaxy clusters may hold hundreds or thousands of individual star systems.

Scientists have yet to identify the catalyst behind cluster formation and have scanned the heavens to understand how galaxy cluster progenitors behaved at the dawn of the universe.

In the study, set to be published Sept. 30 in The Astrophysical Journal, scientists said the 12 newly discovered galaxies – called a protocluster – reveal that star groupings of this size already existed when the universe was just 800 million years old, 6% its present age.

The assembly of galaxies, found within the Cetus constellation, is the earliest ever found and was discovered using the Subaru, Keck, and Gemini Telescopes, the study said.

The previous oldest known cluster was the SDF protocluster, discovered near the constellation Coma Berenices.

Lead researcher Yuichi Harikane of the National Astronomical Observatory of Japan said in a statement that a map of the universe made using the Subaru Telescope was key in identifying the protocluster.

“A protocluster is a rare and special system with an extremely high density, and not easy to find,” Harikane said. “To overcome this problem, we used the wide field of view of the Subaru Telescope to map a large area of the sky and look for protoclusters.”

After identifying the protocluster – designated as z66OD – researchers completed follow-up observations using the W.M. Keck Observatory and Gemini North Telescope.

The grouping of galaxies was later confirmed to have a concentration of star systems 15 times higher than normal, the study found.

Himiko, one of the 12 galaxies, is named after a legendary mythological queen in ancient Japan, according to researchers. University of Tokyo researcher Masami Ouchi discovered Himiko in 2009 using the Subaru Telescope.

Ouchi said in a statement that scientists are unclear why Himiko is not in the center of the protocluster, considering the galaxy’s size.

“We’re surprised to see that Himiko was located not in the center of the protocluster, but on the edge 500 million light-years away from the center,” said Ouchi, also with the National Astronomical Observatory of Japan. “These results will be a key for understanding the relationship between clusters and massive galaxies.”

Researchers found an irony within the protocluster’s design since it is believed that Queen Himiko was reclusive, living outside the domain of her people.

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