Webb discovered the oldest galaxies, their age and properties surprised astronomers

One of these galaxies is observed as it appeared about 300 million years after the Big Bang and shines much brighter than expected. This figure now makes researchers estimate that the first galaxies were formed 100 million years after the Big Bang. "It's like an archaeological dig, when you suddenly find a lost city or something you didn't know about," said one of the researchers

Just days after officially beginning scientific activity, the James Webb Space Telescope of NASA and the European Space Agency has introduced astronomers into the realm of early galaxies, previously hidden beyond the viewing power of all other telescopes, including Hubble.

Webb now reveals a very rich universe where the first galaxies to form look different from the mature galaxies seen around us today. The most important discovery is of two extremely bright galaxies that existed about 300 and 400 million years after the Big Bang. Their extreme brightness is puzzling to astronomers. The young galaxies are turning gas into stars as fast as they can and appear compressed into spherical or disc shapes much smaller than our own Milky Way galaxy. It is possible that the beginning of the birth of stars occurred as early as 100 million years after the big bang, which happened 13.8 billion years ago. 

Within just four days of the publication of the photographs, researchers discovered in them two extremely bright galaxies in the images from the GLASS group of galaxies. These galaxies existed about 450 and 350 million years after the Big Bang (with redshifts of about 10.5 and 12.5, respectively), which Spectroscopic measurements Futures also carried out by Webb will probably help to confirm.

The findings were published in the science program for early release GLASS-JWST  Webb's, and the Cosmic Evolution Rapid Release Science Survey (CEERS). Two research papers, led by Marco Castellano of the National Institute of Astrophysics in Rome, Italy, and Rohan Naidoo of the Center for Astrophysics at Harvard, Smithsonian and the Massachusetts Institute of Technology were published in the Astrophysical Journal Letters.

"We were amazed to find the most distant starlight anyone has ever seen, just days after the researchers published their first data," said Rohan Naidoo. The more distant GLASS galaxy, known as GLASS-z12, is estimated to date back to 350 million years after the Big Bang. The previous record holder was the galaxy GN-z11, which existed 400 million years after the Big Bang (redshift 11.1), and was detected in 2016 by Hubble and the Keck Observatory in the "Deep Sky" observing programs.

"Based on all the predictions, we thought we needed to search a much larger volume of space to find such galaxies," Castellano said.

"Everything we see is new. Webb shows us that there is a very rich universe beyond what we imagined," said Tommaso Tru from the University of California, Los Angeles, a co-investigator in one of the Webb programs. "Once again the universe surprised us. These early galaxies are very unusual in many ways. "

"This is a whole new chapter in astronomy. It's like an archeological dig, when you suddenly find a lost city or something you didn't know about. It's just amazing," added Paola Santini, co-author of the article that relied on Castellano et al. GLASS-JWST.

"While the distances of these galaxies still need to be confirmed by spectroscopy, their extreme brightness is a real puzzle, challenging our understanding of galaxy formation," noted Pascal Och of the University of Geneva in Switzerland.

Webb's observations are bringing astronomers toward a consensus that an unusual number of galaxies in the early universe were much brighter than expected. This will make it easier for Webb to find even more early galaxies in future deep-sky surveys, the researchers say.

"We made a fascinating discovery. These galaxies should have started forming perhaps only 100 million years after the Big Bang. "No one expected the dark age of the universe to end so early," said Gareth Illingworth of the University of California, Santa Cruz. "The initial universe was only a hundredth of its current age. It is a sliver of time in the 13.8 billion year evolving cosmos. "

Naidu/Oesch team member Erika Nelson of the University of Colorado noted that “our team was amazed to be able to measure the shapes of these first galaxies; Their calm and orderly disks cast doubt on our understanding of how the first galaxies formed in the dense and chaotic early universe. "This amazing discovery of compact discs at such early times was only possible because Webb's images are much sharper, in infrared light, than Hubble's."

Small but bright galaxies

"These galaxies are very different from the Milky Way or other large galaxies that we see around us today," Trio said.

Illingworth emphasized that the two bright galaxies that were discovered shine brightly. He said one possibility is that they could have been very massive, with many low-mass stars, like later galaxies. Alternatively, they can be much less massive, and composed of far fewer unusually bright stars, called population III stars. According to the old theory, these were the first stars ever born, burning at high temperatures and composed only of primordial hydrogen and helium; Only later will you develop stars that have "cooked" heavier elements in their nuclear fusion furnaces. Such hot, primordial stars are not seen in the local universe.

"Indeed, the most distant source is very compact, and its colors seem to indicate that its stellar population is devoid of particularly heavy elements and may even contain a few population III stars. Only the spectrum of the web will clarify," said Adriano Fontana, the second author of the paper by Costellono et al. and a member of the GLASS-JWST team.

Webb's current distance estimates for these two galaxies are based on measuring their infrared colors (expressed in redshift). Eventually, subsequent spectroscopic measurements showing how light is stretched in the expanding universe will provide independent verification of these cosmic measurements.

to the announcement of the European Space Agency