Evrim Yazgin
Cosmos science journalist
The James Webb Space Telescope (JWST) has broken yet another record, with astronomers looking at data from the Hubble Space Telescope’s successor and finding the most distant galaxy ever confirmed, to be known as JADES-GS-z13-0.
The previous oldest-known galaxy was discovered by Hubble in July. That galaxy, GN-z11, dates back to 400 million years after the birth of the universe.
Only a week after its first full-colour images of GN-z11 were revealed, JWST broke this record by nearly 100 million years, revealing that GLASS-z13 dates back to only 300 million years after the Big Bang.
In August JWST made headlines again when CEERS-93316 was announced as a galaxy candidate from only 235 million years from the beginning of our cosmos.
But neither the age of GLASS-z13 nor CEERS-93316 is confirmed by the “gold standard” of distance measurements.
This latest discovery, published on the preprint server arXiv, does in fact use the gold-standard approach of spectroscopy to confirm the distance of galaxy candidates. According to the results, galaxy JADES-GS-z13-0 was imaged by Webb as it was 325 million years after the Big Bang.
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Astronomers determine the distance of objects in the universe by their “redshift”. This is essentially a measurement of how the expansion of the universe has stretched the wavelengths of light coming from distant objects.
It is similar in principle to the Doppler effect you hear when an ambulance drives past. As the ambulance gets further away, the siren becomes lower in pitch.
In astronomy, higher redshifts mean that an object is further away because it means the wavelength of light has been stretched more by the universe’s expansion. GN-z11 has a redshift of about z = 10.957.
JADES-GS-z13-0 has a redshift of 13.2.
Astronomers can get reasonably good estimates of redshift by applying specific filters on their cameras. This is called photometry, and is the method used to estimate the redshift of both GLASS-z13 and CEERS-93316. But photometry is not the best way to get an accurate redshift measurement. If a galaxy has a lot of dust in or around it, for example, it can make the object look further away than it really is.
The gold standard is spectroscopy because it splits the light up into its component parts. Astronomers can then determine which wavelengths are coming from stars in the galaxy, and which are coming from dust.
Both JADES-GS-z13-0 and GN-z11 have been confirmed through spectroscopy.
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JADES-GS-z13-0 was discovered as part of the JADES (JWST Advanced Deep Extragalactic Survey) by the UK University of Hertfordshire’s Dr Emma Curtis-Lake and colleagues., The JADES galaxy is now estimated to be 33 billion light years from Earth due the expansion of the universe in the time since the light that has just reached JWST left the galaxy.
“I’m actually in awe and incredibly grateful to be part of this moment,” Curtis-Lake told BBC News.
The ability to get a spectroscopic analysis of JADES-GS-z13-0 and other very distant galaxies is thanks to Webb’s powerful near-infrared spectrometer (NIRSpec) developed by the European Space Agency (ESA).
“This is what JWST was built to do and the European-built NIRSpec instrument lies at the heart of it,” ESA senior scientific advisor Professor Mark McCaughrean told the BBC. “The search for ‘first light’ in the Universe needs a large, cold space telescope and a sensitive infrared camera to identify things that might be faint galaxies forming just a few hundred million years after the Big Bang.”
“But there’s a lot of hay and not many needles, so you have to look at many candidates, smearing out the tiny amount of light from each one into a spectrum and using tell-tale tracers to see if they have the right distance and age. By being able to efficiently examine hundreds of targets at a time, NIRSpec brings a kind of cosmic magnet to the haystack,” McCaughrean explains.