The James Webb Space Telescope (JWST) has discovered not one but two of the earliest and most distant galaxies ever seen, continuing to break the records it previously set.
The furthest galaxy, JADES-GS-z14-0, is seen as it was around 300 million years after the Big Bang, existing at least 100 million years earlier than the previous record holder. That means that the light the JWST saw from this primordial galaxy has been traveling for 13.5 billion years on its way to reach us.
JADES-GS-z14-0 isn't alone, either. It was discovered along with another galaxy, JADES-GS-z14-1, that is almost as far away and takes second place in the ranking of the earliest galaxies ever seen by humanity.
Related: James Webb Space Telescope spots 3 of our universe's earliest galaxies
The announcement of the discoveries, made in Oct. 2023 and Jan. 2024, are the latest developments in the ongoing investigation of cosmic dawn that the $10 billion telescope has facilitated as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. JADES aims to provide vital insights into the ways in which the stars, gas, and black holes were evolving in primordial galaxies when the 13.8 billion-year-old universe was very young.
"These galaxies join a small but growing population of galaxies from the first half billion years of cosmic history where we can really probe the stellar populations and the distinctive patterns of chemical elements within them," team member and Kavli Institute for Cosmology scientist Francesco D’Eugenio said in a statement.
JADES-GS-z14-0 isn't just remarkable for how distant it is from Earth and how early it existed in the cosmos, though. With a width of around 1,600 light-years across, this "cosmic dawn" galaxy is also remarkable for how big and bright it is.
"The size of the galaxy clearly proves that most of the light is being produced by large numbers of young stars, rather than material falling onto a supermassive black hole in the galaxy's center, which would [make it] appear much smaller, "JADES team leader Daniel Eisenstein from the Harvard & Smithsonian's Center for Astrophysics (CfA) said in a separate statement.
The extreme brightness of JADES-GS-z14-0 and the fact this luminosity is powered by young stars means this galaxy represents the most striking evidence for the rapid formation of large, massive galaxies in the early universe found thus far.
JADES team member and University of California-Santa Cruz researcher Ben Johnson added that JADES-GS-z14-0 shows that galaxy formation in the early universe was very rapid and intense.
"The JWST will allow us to find more of these galaxies, perhaps when the universe was even younger," he said. "It is a marvelous opportunity to study how galaxies get started."
The James Webb Space Telescope sees red to spot early galaxies
The JWST is adept at seeing early galaxies thanks to the high infrared sensitivity of its instruments, particularly its primary imager, the Near Infrared Camera (NIRCam).
Light leaves these cosmic dawn galaxies with a wide range of wavelengths similar to light from galaxies that are closer to the Milky Way. It is the journey of billions of years that transforms this light into low-energy and long-wavelength light in the near-infrared and infrared regions of the electromagnetic spectrum.
The very fabric of space is expanding, and as light passes through it, its wavelength is stretched along with it. This causes the light to "shift" down to the red end of the electromagnetic spectrum, hence the name for this phenomenon, "redshift."
Galaxies that are farther away have to cross more space (which is being stretched as it expands) before their light reaches us, and thus, that light experiences more redshift. Redshift, denoted as z, can, therefore, be used to measure the distance to celestial objects with a known spectrum. And because light takes a finite amount of time to travel, this distance can be used to calculate how long ago these galaxies existed as we see them.
JADES-GS-z14-0 has a redshift of z = 14.32, while the previous most distant galaxy, JADES-GS-z13-0, has a redshift of z = 13.2, which placed it as existing 400 million years after the Big Bang. Clearly, this newly found galaxy has absolutely smashed that record, with the JWST seeing back in time by another 100 million years or so.
"JADES-GS-z14-0 now becomes the archetype of this phenomenon," JADES collaboration team member Stefano Carniani of the Scuola Normale Superiore said. "It is stunning that the universe can make such a galaxy in only 300 million years."
JADES-GS-z14-0 delived some surprises
Not everything about JADES-GS-z14-0 was immediately clear to the JADES team and some elements could confuse our picture of the early cosmos.
When it was first spotted, the primordial galaxy was so close to a closer foreground galaxy that the team suspected they could be celestial neighbors. This idea was dispelled in October last year when the JADES crew spent five days performing a deep analysis of JADES-GS-z14-0 with NIRCam. The application of filters that are specifically tailored to identify early galaxies confirmed the extreme distance to JADES-GS-z14-0.
"We just couldn’t see any plausible way to explain this galaxy as being merely a neighbor of the more nearby galaxy," JADES team member and University of Arizona researcher Kevin Hainline said.
The galaxy also surprised its discoverers because its light is even redder than expected. That is because the light from JADES-GS-z14-0 is being "reddened" by dust within it that will become the building blocks of stars that will help this galaxy grow even larger.
Another surprise was the discovery of oxygen in JADES-GS-z14-0. Elements heavier than hydrogen and helium are forged by stars during their lifetimes and then distributed through galaxies when these stars explode. The observation of oxygen in JADES-GS-z14-0 could indicate that at least one generation of stars has already lived and died in this very early galaxy.
"All of these observations, together, tell us that JADES-GS-z14-0 is not like the types of galaxies that have been predicted by theoretical models and computer simulations to exist in the very early universe," JADES researcher Jake Helton of Steward Observatory and the University of Arizona said. "Given the observed brightness of the source, we can forecast how it might grow over cosmic time, and so far, we have not found any suitable analogs from the hundreds of other galaxies we’ve observed at high redshift in our survey."
Helton added that given the relatively small region of the sky that the JWST searched to find JADES-GS-z14-0, its discovery has profound implications for the predicted number of bright galaxies we see in the early universe.
"It is likely that astronomers will find many such luminous galaxies, possibly at even earlier times, over the next decade with the JWST," he concluded. "We're thrilled to see the extraordinary diversity of galaxies that existed at cosmic dawn!”
