Astronomy & Space

The Webb telescope has discovered the earliest galaxies yet viewed.

The four farthest galaxies ever observed have been found by the James Webb Space Telescope, one of which formed just 320 million years after the Big Bang, when the universe was still young.

Since it started operating last year, the Webb telescope has sparked a flood of scientific research while looking farther than ever into the far reaches of the cosmos, which also means it is looking back in time.

By the time light from the farthest galaxies reaches Earth, it has been stretched by the universe’s expansion and moved to the infrared spectrum.

The NIRCam instrument on the Webb telescope has a previously unheard-of capacity to detect this infrared light, enabling it to quickly spot a range of never-before-seen galaxies—some of which could reshape astronomers’ understanding of the early universe.

The four most distant galaxies ever observed have been “unambiguously detected,” according to two studies that were published in the journal Nature Astronomy.

The galaxies were created between 300 and 500 million years after the Big Bang, more than 13 billion years ago, when the universe was only 2% as old as it is today.

That indicates that the galaxies date from a time period known as “the epoch of reionization,” during which the first stars are thought to have formed. The epoch immediately followed the Big Bang-induced cosmic dark ages.

The farthest galaxy, known as JADES-GS-z13-0, was formed 320 million years after the Big Bang, according to Stephane Charlot, a researcher at the Astrophysics Institute of Paris and co-author of the two new studies.

According to him, this is the greatest distance that astronomers have ever recorded.

The Hubble Space Telescope had previously discovered JADES-GS-z10-0, which was discovered 450 million years after the Big Bang. The Webb telescope also confirmed the existence of this object.

According to Charlot, all four galaxies are “very low in mass,” each weighing about 100 million solar masses. According to some estimates, the Milky Way weighs 1.5 trillion solar masses.

However, Charlot noted that the galaxies are “very active in star formation in relation to their mass.”

That rate of star formation, which was “surprising so early in the universe,” was “roughly the same as the Milky Way,” he continued.

Additionally, he said that the galaxies were “very poor in metals.”

This is in line with the standard model of cosmology, which states that the less time there is for the formation of such metals, the closer the universe is to the Big Bang. This model is science’s best explanation of how the universe functions.

A technical triumph.
But in February, six massive galaxies that were discovered between 500 and 700 million years after the Big Bang caused some astronomers to start doubting the standard model.

If confirmed, the standard model may require revision. Those galaxies, which the Webb telescope also observed, were larger than previously thought to be possible so soon after the creation of the universe.

The confirmation of the four recently discovered distant galaxies was praised as a “technical tour de force” by Yale University astronomer Pieter van Dokkum, who was not involved in the most recent research.

Van Dokkum wrote in Nature that “there is only 300 million years of unexplored history of the universe between these galaxies and the Big Bang,” adding that “the frontier is moving almost every month.”

Even though they have not yet been verified, the Webb telescope may have seen galaxies even closer to the Big Bang.

More information: B. E. Robertson et al, Identification and properties of intense star-forming galaxies at redshifts z > 10, Nature Astronomy (2023). DOI: 10.1038/s41550-023-01921-1

Emma Curtis-Lake et al, Spectroscopic confirmation of four metal-poor galaxies at z = 10.3–13.2, Nature Astronomy (2023). DOI: 10.1038/s41550-023-01918-w

Pieter van Dokkum, An exciting era of exploration, Nature Astronomy (2023). DOI: 10.1038/s41550-023-01946-6

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