Scientists analyzing data collected by the James Webb Telescope (JWST) have identified two of the most distant galaxies ever observed. Surprisingly bright considering their age, they are particularly attracting the attention of researchers.
Launched nearly a year ago, NASA’s James Webb Telescope continues to make fascinating observations: a quasar dating from the early universe, a superb shot of the pillars of creation and the discovery of CO2 in the atmosphere of an exoplanet… It should revolutionize our knowledge of the universe and one of its main objectives is precisely the observation of the first galaxies and stars.
The oldest galaxies ever observed
Thanks to two studies published in The Astrophysical Journal Letters on October 18 and November 17 respectively, this area could already benefit from a revolutionary discovery. Indeed, the researchers dated two galaxies observed by the telescope to only 350 and 400 million years after the Big Bang, which occurred around 13.8 billion years ago. They are the most distant, and therefore oldest, galaxies ever observed.
Very old galaxies are identified by the infrared light they emit; they do not appear in the realm of visible light because their light has traveled for so long before reaching us that it has turned red. In this specific case, the researchers examined the images taken by the telescope and selected the galaxies of interest according to their color, they thus chose the galaxies not appearing in the wavelength of visible light, but in the infrared range of the James Webb telescope, which means that they are particularly old.
But despite their distance, the two galaxies are surprisingly bright, which has scientists wondering.
A groundbreaking discovery about the formation of the Universe
Normally, very distant galaxies or stars are not so bright, so such light suggests that the object is particularly massive. The researchers believe that in this case, it is not necessarily true: they rather lean towards the hypothesis of galaxies that are not necessarily massive, but populated by stars of population III, whose existence has not yet been proven.
The latter are, according to the theories of scientists, extremely massive and luminous, made up exclusively of light elements. Above all, they are the first stars formed after the Big Bang, which leads astronomers to review their assumptions about the first stars.
It is estimated that their formation dates from around 400 million years after the Big Bang. If the age of the two galaxies is confirmed, it would mean that the dark ages of the Universe, corresponding to the period when no astrophysical process allowed to produce electromagnetic radiation, did not last as long as predicted. researchers.
” Somehow the universe managed to form galaxies faster and earlier than we thought says Tommaso Treu, principal investigator of one of the James Webb Telescope programs. These observations could thus raise many questions about the nature of stars, their formation as well as the type of stars that formed at the beginning of the universe.
A final examination must be carried out
It should be noted, however, that the age of the stars will not be officially established until they have been subjected to a spectroscopic examination, a field of study in which the JWST specializes, but astronomers must wait for the latter to conduct the many scientific activities already planned for its first year in space.
” Obtaining a spectrum of the source, when we see the emission lines of different elements, tells us exactly what we are looking at. So that’s the element we need to go to. “, explains Jeyhan Kartaltepe, co-author of one of the two studies. Although spectroscopy has not yet confirmed their observation, the researchers remain confident about the great antiquity of the two galaxies.
Sources: The Verge, Space.com, The Astrophysical Journal Letters (1), The Astrophysical Journal Letters (2)
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