JWST has broken the record for most distant galaxy ever confirmed

The James Webb Space Telescope has spotted the most distant galaxy ever definitively confirmed, which formed within about 325 million years of the big bang

By Leah Crane

The James Webb Space Telescope (JWST) has spotted the most distant galaxies ever confirmed. While it has seen many galaxies that seem extraordinarily far away, these are the first ones with evidence proving that they are as distant as they appear.

Astronomers measure the distances to cosmic objects using a metric called redshift. Because of the expansion of the universe, the more distant an object is from Earth, the faster it moves away from us. Similar to the Doppler effect, in which a sound seems to rise or fall in pitch depending on whether it is moving towards or away from the listener, the colour of the light coming from a galaxy becomes redder the faster it is speeding away. By comparing how red a galaxy appears to calculations of its actual colour, astronomers can determine how distant a galaxy actually is.

In early observations of galaxies by JWST, astronomers could only make an approximation of each galaxy’s redshift because they did not have detailed data on the spectra of the light coming from those galaxies. Those observations provided hints of galaxies with redshifts of 12 and above, meaning they seem to be more than 30 million light years away and would have formed within 400 million years of the big bang – but many scientists viewed those findings with scepticism because of the lack of precise confirmation.

“It was crucial to prove that these galaxies do, indeed, inhabit the early universe,” said Emma Curtis-Lake at the University of Hertfordshire in the UK in a NASA blog post. “It’s very possible for closer galaxies to masquerade as very distant galaxies.”

Now, as part of the JWST Advanced Deep Extragalactic Survey (JADES), researchers have confirmed the redshifts of four extremely distant galaxies, ranging from about 10.4 to 13.2. That means that they formed between 325 million and 450 million years of the big bang. The previous record for highest confirmed redshift was about 11.

“These are by far the faintest infrared spectra ever taken,” said Stefano Carniani at Scuola Normale Superiore in Italy. The observations took 28 hours over three days and covered 250 faint galaxies in total, and another set of observations is planned for 2023. It is expected to confirm even more of these distant galaxies, which will teach us about the early days of galaxy formation and how the most distant galaxies differ from those in our cosmic neighbourhood.

Reference: arxiv.org/abs/2212.04480

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