Using the new James Webb Space Telescope (JWST), astronomers have spotted two leading contenders for what could be the most distant galaxy ever seen. Both surfaced in the fray of the preliminary results posted online as preprints in the weeks after the telescope began science operations in July. After undergoing intense scrutiny, including reassessment due to updated telescope calibration, the results are now among the first JWST discoveries about the early universe to be published in assessed reports. by peers.^1,2.

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Researchers have yet to confirm the distances of these galaxies by analyzing the spectral properties of the light they emit. But if early estimates are correct, the light from these objects has traveled such great distances that they appear as they were just 350 to 450 million years after the Big Bang. Together with other findings from the JWST, these observations indicate that galaxies formed and evolved earlier in the history of the Universe than astronomers have been able to probe until now.

“It was a bit surprising that so many formed so early,” says Jeyhan Kartaltepe, an astronomer at the Rochester Institute of Technology in New York. And it challenges notions about how galaxies formed in the early Universe, she says.

Like many distant galaxies spotted by the telescope, the two farthest contenders appear small and bright, suggesting they are compact, disc-shaped objects rather than diffuse and scattered. Their order and luminosity suggest that early galaxies had already developed well-organized structures from many stars, rather than being distorted and faint as earlier studies with the Hubble Space Telescope had indicated.

“It’s amazing – we see such bright galaxies in early times,” said Garth Illingworth, author of one of the new reports and an astronomer at the University of California, Santa Cruz, during a press briefing. November 17.

A race for the record

JWST, a US$10 billion observatory, studies the Universe in infrared wavelengths. One of its specialties is being able to detect light from distant galaxies that has been stretched to redder wavelengths by the expansion of the Universe. Astronomers use a measurement known as the redshift to describe exactly how far apart galaxies are, with higher redshifts indicating more distant objects. One of the now-published distant galaxy candidates has a redshift of 10.4 or 10.6, and the second candidate has a redshift of 12.2 or 12.4. The latter beats the previous record: a galaxy with a redshift of about 11, spotted by Hubble³.

The final published redshifts are slightly lower than those reported in previous preprints. Like many early JWST results, the results have been extensively recalculated after the Space Telescope Science Institute in Baltimore, Maryland, released updated data calibrations for the telescope from late July.

Many other JWST distant galaxy candidates are still going through the peer review process. Some might surpass the new record holder at redshift 12.4. At least one has already been confirmed by spectroscopy at redshift 9.76, in a preprint published October 27 on arXiv.org⁴. This preprint is listed as having been submitted to Nature.

Meanwhile, scientists are studying more broadly what the telescope reveals about galaxy formation. In a preprint published on November 10⁵, a team including Kartaltepe analyzed 26 galaxies observed by the telescope with preliminary redshifts of 9 to 16. This work also shows that there are many more bright galaxies at these distances than theory had predicted. . “Although it is in its early days with JWST,” the authors write, “[initial] the results provide exciting insight into the potential secrets of the early universe that our observations may reveal.