An international team of astronomers has made a groundbreaking discovery with the identification of the two earliest and most distant galaxies ever observed, dating back to just 300 million years after the Big Bang. This significant milestone in the study of the early universe was achieved using NASA's James Webb Space Telescope (JWST).
The discoveries were facilitated by the JWST Advanced Deep Extragalactic Survey (JADES) team. Daniel Eisenstein, from the Center for Astrophysics | Harvard & Smithsonian (CfA), leads the JADES team and is the Principal Investigator of the observing program that revealed these ancient galaxies. Key contributions were also made by Ben Johnson and Phillip Cargile, both Research Scientists at CfA, and Zihao Wu, a Harvard Ph.D. student at CfA.
Due to the universe's expansion, the light from these distant galaxies stretches to longer wavelengths as it travels through space. This stretching, or redshift, is so pronounced for these galaxies that their ultraviolet light has been shifted to infrared wavelengths, detectable only by the JWST. As light takes time to travel, observing these distant galaxies allows astronomers to see them as they were in the distant past.
The two newly discovered galaxies have been designated JADES-GS-z14-0 and JADES-GS-z14-1, with JADES-GS-z14-0 being the more distant of the two. JADES-GS-z14-0 not only sets a new record for distance but also stands out for its significant size and brightness.
“The size of the galaxy clearly proves that most of the light is being produced by large numbers of young stars,” explained Eisenstein, a Harvard professor and chair of the astronomy department. “This suggests that the light is not from material falling onto a supermassive black hole in the galaxy's center, which would appear much smaller.”
The combination of extreme brightness and the light from young stars makes JADES-GS-z14-0 compelling evidence of the rapid formation of large, massive galaxies in the early universe.
“JADES-GS-z14-0 now becomes the archetype of this phenomenon,” stated Dr. Stefano Carniani of the Scuola Normale Superiore in Pisa, the lead author of the discovery paper. “It is stunning that the universe can make such a galaxy in only 300 million years.”
Evidence for unexpectedly vigorous early galaxies appeared in the first JWST images and has been growing during the mission's first two years. This trend contradicts the pre-launch expectations of many astronomers regarding galaxy formation theories.
Initially, JADES-GS-z14-0 puzzled the JADES team when they first observed it over a year ago, as it appeared close on the sky to a foreground galaxy, making it challenging to determine if they were neighbors. However, in October 2023, the JADES team conducted deeper imaging—five full days with the JWST Near-Infrared Camera on one field—and used specialized filters to better isolate the earliest galaxies.
“We just couldn't see any plausible way to explain this galaxy as being merely a neighbor of the more nearby galaxy,” said Dr. Kevin Hainline, a research professor at the University of Arizona.
The galaxy is located in a field where the JWST Mid-Infrared Instrument had conducted an ultra-deep observation. Its brightness at intermediate infrared wavelengths signals emission from hydrogen and oxygen atoms in the early universe.
“Despite being so young, the galaxy is already hard at work creating the elements familiar to us on Earth,” noted Zihao Wu, a co-author of a second paper on this discovery, led by Jakob Helton, a graduate student at the University of Arizona.
Encouraged by their findings, the team obtained spectra of each galaxy, confirming that JADES-GS-z14-0 was indeed a record-breaking galaxy and that the fainter candidate, JADES-GS-z14-1, was nearly as distant.
A third paper, led by Brant Robertson, a professor at the University of California-Santa Cruz, and Ben Johnson, examines the evolution of this early population of galaxies.
“This amazing object shows that galaxy formation in the early universe is very rapid and intense,” said Johnson. “JWST will allow us to find more of these galaxies, perhaps when the universe was even younger. It is a marvelous opportunity to study how galaxies get started.”
All three papers detailing these discoveries are currently available on the arXiv preprint server.
Source: Harvard-Smithsonian Center for Astrophysics