Webb telescope discovers oldest galaxies ever observed

The James Webb Space Telescope has discovered the four most distant galaxies ever observed, one of which formed just 320 million years after the Big Bang, when the universe was still in its infancy, new research said Tuesday.

The Webb telescope has unleashed a torrent of scientific discoveries since it went online last year, looking farther than ever into the far reaches of the universe, which also means it's looking back in time.

For when the light from the farthest galaxies reaches Earth, has been stretched by the expansion of the universe, and has moved into the infrared region of the light spectrum.

The Webb Telescope's NIRCam instrument has an unprecedented ability to detect this infrared lightallowing it to rapidly detect a variety of never-before-seen galaxies, some of which could reshape astronomers' understanding of the primitive universe.

In two studies published in the nature astronomy Journal, astronomers revealed that they have "unambiguously detected" the four most distant galaxies ever observed.

The galaxies date from 300 to 500 million years after the Big Bang, more than 13 billion years ago, when the universe was only two percent of its current age.

That means the galaxies are from what is called "the epoch of reionization," a period in which the first stars they are believed to have arisen. The epoch came directly after the cosmic dark ages triggered by the Big Bang.

'Amazing'

Stephane Charlot, a researcher at the Paris Institute of Astrophysics and co-author of the two new studies, told AFP that the farthest galaxy, called JADES-GS-z13-0, formed 320 million years after the Big Bang.

That is the greatest distance ever observed by astronomers, he said.

The Webb Telescope also confirmed the existence of JADES-GS-z10-0, which dates to 450 million years after the Big Bang and had been previously detected by the Hubble Space Telescope.

All four galaxies are "very low in mass," weighing in at about a hundred million solar masses, Charlot said. The Milky Way, for comparison, weighs 1.5 trillion solar masses according to some estimates.

But galaxies are "very active in star formation in proportion to its mass," Charlot said.

Those stars were forming "at roughly the same rate as the Milky Way," a rate that was "astonishing so early in the Universe," he added.

The galaxies were also "very metal poor," he added.

This is consistent with the standard model of cosmology, the best scientific understanding of how the universe works, which says that the closer to the Big Bang, the less time there is for such metals to form.

technical tour de force

However, in February, the discovery of six massive galaxies 500 to 700 million years after the Big Bang led some astronomers to question the standard model.

These galaxies, also observed by the Webb telescope, were larger than thought possible shortly after the birth of the universe; if confirmed, the standard model might need an upgrade.

Pieter van Dokkum, a Yale University astronomer who was not involved in the latest research, hailed the confirmation of the four newly discovered distant galaxies as a "technical tour de force."

"The frontier moves almost every month," van Dokkum commented in Nature, adding that there was now "only 300 million years of unexplored history of the universe between these galaxies and the Big Bang."

The Webb telescope has observed possible galaxies even closer to the Big Bang, but they have not yet been confirmed, he said.

© 2023 AFP