The Webb telescope discovers the oldest galaxies ever observed

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

The Webb telescope has unleashed an avalanche of scientific discoveries since it became operational last year, peering further than ever into the distant reaches of the universe — which also means it’s looking back in time.

By the time the light from the most distant galaxies reaches Earth, it has been stretched by the expansion of the universe and shifted into the infrared region of the light spectrum.

The Webb telescope’s NIRCam instrument has an unprecedented ability to detect this infrared light, allowing it to spot a range of galaxies never before seen–some of which could reshape astronomers’ understanding of the early universe.

In two studies published in natural astronomy In the journal, astronomers reveal that they have “unequivocally discovered” the four most distant galaxies ever observed.

Galaxies date back 300 to 500 million years after the Big Bang more than 13 billion years ago, when the universe was only 2% of its current age.

This means that the galaxies are in what is called an “era of reionization,” the period when the first stars are thought to have appeared. This era came after the cosmic dark ages brought about by the Big Bang.

a surprise

The most distant galaxy called JADES-GS-z13-0 formed 320 million years after the Big Bang, Stéphane Charlotte, a researcher at the Institute of Astrophysics in Paris and co-author of the two new studies, told AFP.

He said that this is the largest distance that astronomers have ever observed.

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

All four galaxies are “extremely low mass,” said Charlotte, weighing nearly a hundred million solar masses. In comparison, the Milky Way weighs 1.5 trillion solar masses by some estimates.

The galaxies are “very active in forming stars in proportion to their mass,” Charlotte said.

He added that those stars were forming “at the same rate as the Milky Way,” a speed that was “surprisingly early in the universe.”

He added that the galaxies were also “very poor in minerals”.

This aligns with the Standard Model of cosmology, the best scientific understanding of how the universe works, which says that the closer we get to the Big Bang, the less time there is for such minerals to form.

Artistic tour de force

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

These galaxies, also spotted by the Webb telescope, were larger than thought soon after the birth of the universe – if confirmed, the Standard Model may need to be updated.

Peter van Dokkum, a Yale 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 boundary moves about every month,” Van Dokkum commented in Nature, adding that “there are now only 300 million years of unexplored history of the universe between these galaxies and the Big Bang.”

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

© 2023 AFP