In the very first observations of the new spacecraft, astronomers have found two galaxies, including the most distant and therefore oldest known, formed just 300 million years after the Big Bang.
And boom! Just a few weeks after the start of its scientific observations, the new James Webb Space Telescope (JWST) appears to have already broken a record: the record for the most distant galaxy ever observed… which is therefore also the oldest because the further you look in the universe, the further back in time you go. If the astrophysicists responsible for its discovery were correct, JWST has captured light from a galaxy that was ejected just 300 million years after the Big Bang. This is 100 million years less than the previous record, which was established in 2016 thanks to the Hubble telescope.
James Webb was launched at Christmas and first went through a long deployment and calibration phase. He just started his scientific observations in July (where he reveals gorgeous images of galaxies and nebulae to show what he’s capable of). And the first astronomers are already working on the collected data. This is how an international team of 25 researchers was able to dissect a “deep field” photographed by JWST, that is, a very small part of the sky where we can detect the faint glow of the galaxies further away with a sufficiently long exposure time.
Astronomers describe in a study the two oldest galaxies they discovered there. One, dubbed Glass-z11, is just as distant as the previous record from 2016. The other, Glass-z13, is even further and older.
How do we know these galaxies are the most distant we know? Just measure their color. Or more precisely the wavelengths of light they emit. The further the galaxy is within the bounds of the expanding universe and expanding spacetime since the Big Bang, the more its light appears to us to be redshifted when it arrives at Earth. Astrophysicists measure this redshift – red shift in English – and quantify it. Thus, the galaxy Glass-z11 has a redshift of 11, and the record galaxy Glass-z13 has a redshift of 13.
To capture them, a classic camera is not enough. The James Webb telescope specializes in infrared observation, which will make it an excellent spotter of ancient redshifted galaxies. It has several sensors with different characteristics, and here in this case it is the Nircam instrument (near infrared camera) that caught the light of the progenitor galaxies. This is a camera made by the University of Arizona that captures wavelengths longer than the red visible to our eyes.
What do Glass-z11 and Glass-z13 tell us? “They look pretty massive” And this “very shortly after the Big Bang”, comments to AFP, the lead author of the study, the young American astrophysicist Rohan Naidu. It’s quite unexpected: how could they have collected so much matter at such an early point in the universe’s history? This will perhaps be better understood when James Webb finds other similar objects of study. Which was bound to happen as he so quickly revealed his first feat. Galaxies that old and visible from Earth don’t seem that unusual. When the previous record-breaking galaxy was discovered in 2016, “a key question was whether she was eccentric or had a family… I’m now betting on the second option!” sums up Rohan Naidu on Twitter.
So far, the study is only pre-published – that is, it has become available to the community, but has not yet been reviewed and peer-reviewed for publication in a scientific journal. But another team of astrophysicists led by the Italian Marco Castellano came to the same conclusions, giving hope that the discovery is valid. Thomas Zurbuchen, Director of the Science Division at NASA, cannot hide his excitement on Twitter: “Astronomical records are already beginning to fall,” he is looking forward and betting that this is the first in a long line.