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Friday, July 12, 2024 | Back issues
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Astronomers observe pair of merging quasars, just 900 million years after Big Bang

A team of astronomers discovered the rare event by accident.

(CN) — A pair of quasars merged nearly 13 billion years ago — only a scant 900 million years after the Big Bang that created the universe — in the most distant such event ever observed by astronomers.

As reported by astronomers in a study describing the distant quasar merger, published Monday in the Astrophysical Journal Letters, the merger is the first that has been observed occurring during the period known as the Cosmic Dawn, which spanned from about 50 million years to one billion years after the birth of the universe, in which the first stars and galaxies started appearing.

Within that period, from 400 million years after the Big Bang onward, was what astronomers call the Epoch of Reionization, when light from the first stars, galaxies and quasars began to light up the universe, ending what is sometimes called the cosmic dark ages.

Quasars — extremely luminous galactic cores — are among the brightest objects in the universe. Astronomers are curious about the role they played in the early formation of the universe. They have observed 30 quasars during the Epoch of Reionization, but never before a pair merging.

“The existence of merging quasars in the Epoch of Reionization has been anticipated for a long time. It has now been confirmed for the first time," Yoshiki Matsuoka, an astronomer at Ehime University in Japan and lead author of the paper, said in a statement.

He added: “The statistical properties of quasars in the Epoch of Reionization tell us many things, such as the progress and origin of the reionization, the formation of supermassive black holes during Cosmic Dawn, and the earliest evolution of the quasar host galaxies."

This image, taken with the Hyper Suprime-Cam on the Subaru Telescope, shows a pair of quasars in the process of merging (NOIRLab/NSF/AURA/T.A. Rector, D. de Martin and M. Zamani)

Matsuoka and his team discovered the merger by accident. They were reviewing images from the Subaru Telescope, when, they say, they noticed a faint patch of red.

“While screening images of quasar candidates I noticed two similarly and extremely red sources next to each other,” said Matsuoka. “The discovery was purely serendipitous.”

They were able to confirm the sighting with data from the Subaru Telescope and the Gemini North telescope, both of which are located on top of Mauna Kea on the Island of Hawaii.

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