The James Webb Space Telescope may have already found the oldest galaxy ever seen

Just a week after its first images were shown to the world, the James Webb Space Telescope may have found a galaxy that existed 13.5 billion years ago, a scientist who analyzed the data said Wednesday.

Known as GLASS-z13, the galaxy dates back 300 million years after the Big Bang, about 100 million years earlier than anything previously identified, Rohan Naidu of the Harvard Center for Astrophysics told AFP.

“We are potentially looking at the farthest starlight anyone has ever seen,” he said.

The farther the objects are from us, the longer it takes their light to reach us, so looking back into the distant universe means seeing into the deep past.

Although GLASS-z13 existed in the first era of the Universe, its exact age remains unknown as it could have formed at any time within the first 300 million years.

GLASS-z13 was spotted in so-called “early release” data from the orbiting observatory’s main infrared imager, called NIRcam, but the discovery was not revealed in the first set of images released by NASA last week.

When translated from infrared to the visible spectrum, the galaxy appears as a red spot with white in the center, as part of a larger image of the distant cosmos called a “deep field”.

Naidu and colleagues, a team of 25 astronomers from around the world, presented their findings to a scientific journal.

For now, the research is published on a prepress server, so it comes with the caveat that it has yet to be peer-reviewed, but it has already stirred up the global astronomical community.

“Astronomy records are already crumbling and others are shaky”, tweeted NASA chief scientist Thomas Zurbuchen.

“Yes, I tend to cheer only when the science gets a clear peer review. But it looks very promising,” he added.

Naidu said another team of astronomers led by Marco Castellano who worked on the same data reached similar conclusions, “so this gives us confidence.”

‘Work to do’

One of Webb’s great promises is its ability to find the first galaxies that formed after the Big Bang 13.8 billion years ago.

Because these are so distant from Earth, when their light reaches us, it has been stretched by the expansion of the Universe and moved into the infrared region of the light spectrum, that Webb is able to detect with unprecedented clarity.

Naidu and colleagues analyzed these infrared data from the distant Universe, looking for a telltale signature of extremely distant galaxies.

Below a certain infrared wavelength threshold, all photons – packets of energy – are absorbed by the neutral hydrogen of the Universe which lies between the object and the observer.

Using data collected through different infrared filters aimed at the same region of space, they were able to detect where these drop-offs in photons occurred, from which they inferred the presence of these more distant galaxies.

“We looked in all the early data for galaxies with this very surprising signature, and these were the two systems that had by far the most convincing signature,” said Naidu.

One of these is GLASS-z13, while the other, less ancient, is GLASS-z11.

“There is strong evidence, but there is still work to be done,” Naidu said.

Specifically, the team wants to ask Webb’s managers for the telescope’s time to perform spectroscopy, an analysis of light that reveals detailed properties, to measure its precise distance.

“Right now, our guess for distance is based on what we don’t see – it would be great to have an answer for what we see,” said Naidu.

However, the team has already taken over some surprising properties.

For example, the galaxy is the mass of a billion Suns, which is “potentially very surprising, and it’s something we don’t really understand” given how soon after the Big Bang formed, Naidu said.

Launched last December and fully operational last week, Webb is the most powerful space telescope ever built, with astronomers confident it will herald a new era of discovery.

© Agence France-Presse

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