Astronomers have confirmed that four ancient galaxies detected by the James Webb Space Telescope in its first months of operation are the oldest scientists have ever seen and nearly as old as the universe itself.
The galaxies were among hundreds of promising stellar conglomerates found in images from the Near Infrared Camera (NIRCam) aboard the James Webb Space Telescope (Webb or JWST). But scientists could only confirm that these ancient objects were really as old as they appeared after examining them in detail with the Near infrared spectrographwhich revealed their chemical composition and determined how fast these galaxies are moving away from Webb.
Astronomers now know that light from the four galaxies took more than 13.4 billion years to reach Webb. Specifically, the telescope sees galaxies as they were only 350 million years after the big Bangwhen the universe was only 2% of its current age, although galaxies must have started forming even earlier.
Related: James Webb Space Telescope Reveals Universe’s First Galaxies Like Never Before, Scientists Say
Observing such young stellar families is exactly what Webb was built for, and scientists are thrilled that he started delivering such fascinating results so early in his operations.
“These [galaxies] are far beyond what we could have imagined finding before JWST,” said Brant Robertson, an astrophysicist at the University of California, Santa Cruz and one of the researchers involved in the observations, in a statement. “With JWST , for the first time, we can now find galaxies this far away and then confirm by spectroscopy that they really are so far away.”
To confirm that the galaxies really were as old as they seemed, astronomers had to get precise estimates of the so-called red shift from NIRspec data. The redshift makes objects receding from us redder due to the expansion of the universe, which stretches the light emitted by distant stars and galaxies into longer, redder wavelengths. of the light spectrum.
The most distant of the galaxies detected by Webb displayed a redshift of 13.2, which corresponds to an age of about 13.5 billion years – the oldest ever measured for a galaxy.
“At redshift 13, the universe is only about 325 million years old,” Robertson said.
The observations were conducted as part of the JWST Advanced Deep Extragalactic Survey (JADES) project, which uses NIRCam and NIRSpec to study the early universe in ways that were previously impossible.
An international collaboration of more than 80 astronomers, JADES is only at the beginning of its efforts. Next, astronomers want to look at individuals stars in these galaxies, some of which may have been born up to 100 million years before the age at which they are seen by Webb.
“With these measurements, we can know the intrinsic luminosity of galaxies and determine how many stars they have,” Robertson said. “Now we can start to really distinguish how galaxies are assembled over time.”
The observations match what astronomers expected based on existing models of galaxy formation, Robertson added.
In the NIRCam observations, the team also identified galaxies that appear even older than those now confirmed, but the age of these has yet to be verified by NIRSpec’s more precise spectroscopic measurements.
The new findings will be presented Monday (December 12) at a Space Telescope Science Institute conference in Baltimore.
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