James Webb Space Telescope Finds Two Of The Universe's Farthest And Oldest Galaxies: Know Everything

Webb has discovered two exceptionally bright galaxies that existed approximately 350 and 450 million years after the Big Bang. They were found in the outer regions of the galaxy cluster Abell 2744. 

The two bright galaxies have a lot of light, and the reason behind this is that they could have been very massive, with lots of low-mass stars, like later galaxies, or they could be much less massive, consisting of far fewer extraordinarily bright stars, known as Population III stars. ( Image Source :NASA/ESA/CSA via UC Santa Cruz )

NASA's James Webb Space Telescope, which has officially started science operations, has revealed two of the farthest and earliest galaxies in the universe. The "unexpectedly rich realm of early galaxies" has been largely hidden until now, beyond the reach of other telescopes, the University of California, Santa Cruz, says on its website. Webb has discovered two exceptionally bright galaxies that existed approximately 350 and 450 million years after the Big Bang. These and other observations are making astronomers believe that an unusual number of galaxies in the early universe were much brighter than expected. 

Two research papers describing the findings were recently published in the Astrophysical Journal Letters. One of the papers was led by Marco Castellano of the National Institute for Astrophysics in Rome, Italy, while the other paper was led by Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology in Cambridge, Massachusetts. Garth Illingworth, professor emeritus of astronomy and astrophysics at UC Santa Cruz, is a co-author of the paper written by Naidu et al. 

The two galaxies started coming together 100 million years after Big Bang

In the university statement, Illingworth said the galaxies discovered by Webb would have started coming together maybe just 100 million years after the Big Bang, and nobody expected that the dark ages would have ended so early. He added that the primal universe would have been just one-hundredth of its current age, a sliver of time in the 13.8-billion-year-old evolving cosmos. 

The astronomers made these discoveries as part of a JWST research involving two Early Release Science (ERS) programs, namely the Grism Lens-Amplified Survey from Space (GLASS), and the Cosmic Evolution Early Release Science Survey (CEERS). 

Where are the two galaxies located?

Researchers conducted an analysis for just four days, and found the two exceptionally bright galaxies in the GLASS-JWST images. The galaxies existed approximately 450 and 350 million years after the Big Bang, and future spectroscopic measurements are required with Webb to confirm their distances. 

The two galaxies were found in the outer regions of the giant galaxy cluster Abell 2744. 

The extreme brightness of the galaxies are a real puzzle, challenging astronomers' understanding of galaxy formation, according to Pascal Oesch, second author on the Naidu et al. paper.

Referring to the more distant GLASS galaxy in the outer regions of Abell 2744, called GLASS-z12, Naidu said with Webb, the researchers were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data. GLASS-z12 is believed to date back to 350 million years after the Big Bang. 

GN-z11, which existed 400 million years after the Big Bang, was the previous record holder. It was identified in 2016 by Hubble and Keck Observatory in deep-sky programs. 

The discovery of galaxies with compact disks at such early times was another surprise for astronomers. This was only possible because of Webb's much sharper images, in infrared light, compared to Hubble. 

Erica Nelson of the University of Colorado, another team member, said the researchers were struck by being able to measure the shapes of these first galaxies. The calm, orderly disks of the galaxies question astronomers' understanding of how the first galaxies formed in the crowded, chaotic early universe. 

Tommaso Treu from the University of California, Los Angeles, a principal investigator on one of the Webb programs, said Webb is showing the world there is a very rich universe beyond what was imagined, and once again, the universe has surprised researchers, because the early galaxies are very unusual in many ways. 

Why are the two galaxies exceptionally bright?

According to Illingworth, the two bright galaxies have a lot of light, and the reason behind this is that they could have been very massive, with lots of low-mass stars, like later galaxies, or they could be much less massive, consisting of far fewer extraordinarily bright stars, known as Population III stars. Population III stars, which have been theorised for a long time, would be the first stars ever born.

These stars blaze at blistering temperatures and are made up of only primordial hydrogen and helium. Population III stars are extremely hot, primordial stars seen in the local universe. 

Adriano Fontana, second author on the paper led by Castellano et al., said the farthest source is very compact, and its colours seem to indicate that its stellar population is particularly devoid of heavy elements and could even contain some Population III stars.

According to the study, present Webb distance estimates to the two galaxies have been made by measuring their infrared colours. Later on, measurements will be conducted to determine how light has been stretched in the expanding universe. 

Illingworth said the secrets of the earliest galaxies are now only starting to be revealed by Webb, and that the real discoveries lie ahead.