JADES-GS-z13-0, the most distant galaxy captured by the James Webb telescope

The James Webb Space Telescope located the most distant galaxy detected to date, created during the initial expansion of the universe, “just” 320 million years after the Big Bang, according to studies published today.

The first results from the James Webb Telescope (JWST), which began operating in July 2022, identified numerous “candidate” galaxies in the infrared spectrum, a wavelength invisible to the human eye that allows us to go back much further in time.

The further away the galaxies are, the more difficult they are to detect, since their light signal is very poor.

But the telescope has powerful infrared observation capabilities, which combined with spectroscopy, which analyzes light from an object to determine its chemical elements, “unambiguously” located the existence of four galaxies.

All of them are located at the red end of the spectrum, that is, they are very far away, with an age ranging between 300 and 500 million years after the Big Bang (which occurred 13.8 billion years ago), according to two published studies. in Nature Astronomy.

At that time, the universe was only 2% of its current age and was going through what scientists call a period of reionization: after the period known as the “dark ages”, it became active again and began to produce a large amount of stars.

The most distant galaxy located by the JWST, baptized JADES-GS-z13-0, formed “320 million years after the Big Bang” and its light is the most distant observed to date by astronomers, he explained to the agency of AFP news Stéphane Charlot, from the Institute of Astrophysics in Paris, one of the authors of the study.

“Afeat”

The space telescope also confirmed the existence of the galaxy GM-z11, about 450 million years after the Big Bang, which had already been detected by the Hubble telescope.

The four observed galaxies are very low-massive: barely a hundred million solar masses, compared to 1.5 trillion for the Milky Way. Instead, they are “very active when it comes to forming stars, in proportion to their mass”, details the astrophysicist.

Star formation is taking place “at approximately the same rate as the Milky Way,” a speed “astonishing at that early stage of the universe,” says Charlot.

On the other hand, these galaxies are “very metal poor”, a discovery that confirms the usual theories of cosmology: the closer to the origin of the universe, the less time these stars had to form complex molecules.

This new contribution from the JWST is “a technological feat,” says Pieter van Dokkum, an astronomer at Yale University, in a commentary attached to the study. “Every month” the telescope pushes “the frontiers of exploration,” he explains.

Last February, the James Webb located a group of six galaxies 500 to 700 million years old after the Big Bang, apparently much more massive than expected. If the existence of these galaxies were confirmed by spectroscopy, that could call into question some of the theories about the formation of the universe.

The mission of the James Webb

The Webb Space Telescope is an international mission led by NASA, ESA and the Canadian space agency. Launched into orbit on Christmas Day 2021 and eventually placed 1.5 million kilometers from Earth, it cost $10 billion and took three decades to build.

JWST was launched aboard the Ariane rocket from the Kourou spaceport in French Guiana, with the mission of searching for the first stars that illuminated the cosmos.

Equipped with a 6.5 meter wide mirror and four highly sensitive instruments, Webb attempts to detect light that has been traveling through the vastness of space for more than 13.5 billion years.

In that quest, he looks at just about everything there is to see beyond Earth: from icy moons and comets in our own solar system to the colossal black holes that reside at the centers of all galaxies.

So far, it has already captured historic images of Mars, Jupiter, exoplanets, as well as the galaxy cluster SMACS 0723.

The Webb was developed to see all its targets in a very particular way: in the infrared spectrum. Its predecessor, Hubble, had been designed to be predominantly sensitive to light in the optical or visible wavelengths, the same type of light that we detect with our eyes.

Instead, the JWST can detect longer wavelengths, which, although invisible to our eyes, are exactly where the brightness of the most distant objects in the universe will appear.

With information from the AFP agency and BBC