Astronomers announced that they have discovered what could be some of the first galaxies to form in the universe, a tantalizing discovery made because of NASA’s new flagship, the James Webb Space Telescope.
“This is the very first big sample of candidate galaxies outside the range of the Hubble Space Telescope,” astronomer Haojing Yan said at a news conference at the American Astronomical Society meeting in Seattle yesterday. Yan, who happens to be at the University of Missouri, led the recently published study. As the much more sensitive JWST is able to see further into space as compared to its Hubble predecessor, it is basically looking more back in time. In the new catalog of 87 galaxies astronomers have found, some could date directlyto about 13.6 billion years ago, just 200 million years after the Big Bang. Galaxies then emitted the light we come across today, although these systems of stars, gas, and dust would have changed drastically in case they still existed.
Even though scientists are examining different distant galaxies dating from the time the universe was young, the discoveries by Yan and his colleagues could break those records by a few hundred million years. At this time however, they are virtually all still considered candidate galaxies, meaning their birth dates have yet to be established.
To date a galaxies can be a tough proposition: It calls for measuring its “redshift,” how much of the light it emits is stretched toward longer white wavelengths, telling astronomers how fast the galaxy is expanding away from us in the rapidly expanding universe. As a result, that tells astronomers the distance of the galaxies from the Earth, or more precisely, the distance photons from its stars needed to move at the speed of light prior to obtaining a near-Earth space telescope such as the JWST. The light from the stars in the most distant galaxy in this compilation might have been emitted a while before, some 13.6 billion yrs ago, shortly after the young galaxy formed.
These new estimated distances need to be verified using spectra, meaning measuring the light that galaxies give off across the electromagnetic spectrum and determining its distinctive signature. Nevertheless, Yan thinks that several of them are going to be dated properly to the early days of the universe. He mentioned: “I’ll bet $20 and a large beer that the success rate is going to be greater than 50 percent.
The group of Yan observed these galaxies at 6 near infrared wavelengths using JWST’s NIRCam. Astronomers employed a standard “Dropout” technique to compute their distances: The hydrogen gas which surrounds galaxies absorbs light at a certain wavelength, so the wavelengths at which an object is seen or is not visible set a limit on the distance it’s likely to be taken out. These 87 candidate galaxies mostly look like blobs that can only be seen in the longer (and therefore redder) near-infrared wavelengths which can be detected by NIRCam, which could mean they’re very distant and therefore very old.
Nevertheless, it’s possible that a few of them are much closer than anticipated – which would suggest that they’re not really that old after all. Their light, as an instance, could be too weak to detect at some wavelengths. Until Yan can obtain more detailed data, he will not know for certain.