The James Webb Space Telescope (JWST) has discovered not one but two of the earliest and most distant galaxies ever discovered, continuing to break the records it previously set.
The most distant galaxy, JADES-GS-z14-0, is seen as it was about 300 million years after the Big Bang and existed at least 100 million years earlier than the previous record holder. That means the light the JWST saw from this primordial galaxy has been traveling to us for 13.5 billion years.
JADES-GS-z14-0 is not alone either. It was discovered along with another galaxy, JADES-GS-z14-1, which is almost as distant and ranks second among the earliest galaxies ever seen by humanity.
Related: James Webb Space Telescope sees three of the earliest galaxies in our universe
The announcement of the discoveries, made in October 2023 and January 2024, are the latest developments in the ongoing cosmic dawn research that the $10 billion telescope has made possible as part of the JWST Advanced Deep Extragalactic Survey (JADES) program . JADES aims to provide crucial insights into the ways in which stars, gas and black holes evolved in primordial galaxies when the 13.8 billion-year-old universe was still 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 investigate the stellar populations and the distinctive patterns of chemical elements within them,” said team member and Kavli Institute for Cosmology- scientist Francesco D’. Eugenio said in a statement.
However, JADES-GS-z14-0 is notable not only for its distance from Earth and how early it existed in the cosmos. Measuring about 1,600 light-years across, this ‘cosmic dawn’ galaxy is also notable for its size and brightness.
‘The size of the galaxy clearly proves that most of the light is produced by large numbers of young stars, and not by material falling on a supermassive black hole at the center of the galaxy. [make it] appear much smaller,” JADES team leader Daniel Eisenstein of the Harvard & Smithsonian’s Center for Astrophysics (CfA) said in a separate statement.
The extreme brightness of JADES-GS-z14-0 and the fact that this brightness is driven by young stars means that this galaxy represents the most striking evidence for the rapid formation of large, massive galaxies in the early Universe yet discovered. found it.
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 younger,” he said. “It’s a great opportunity to study how galaxies form.”
The James Webb Space Telescope sees red to discover early galaxies
The JWST is adept at seeing early galaxies thanks to the high infrared sensitivity of its instruments, especially its primary image sensor, the Near Infrared Camera (NIRCam).
Light leaves these cosmic dawn galaxies with a wide wavelength range, similar to light from galaxies closer to the Milky Way. It is the journey of billions of years that transforms this light into low-energy, long-wavelength light in the near-infrared and infrared regions of the electromagnetic spectrum.
The fabric of space expands, and as light passes through it, its wavelength stretches with it. This causes the light to “shift” toward the red end of the electromagnetic spectrum, hence the name for this phenomenon, “red shift.”
Galaxies that are further away have to cross more space (which is stretched as it expands) before their light reaches us, and so that light experiences more redshift. Redshift, denoted z, can therefore be used to measure the distance to celestial bodies 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 = 2:32 p.m, while the previous, most distant galaxy, JADES-GS-z13-0, has a redshift of z = 13.2, in which it was considered to have existed 400 million years after the Big Bang. Clearly, this newly found galaxy has absolutely shattered that record, with the JWST able to look back in time another 100 million years or so.
“JADES-GS-z14-0 is now becoming the archetype of this phenomenon,” said Stefano Carniani, member of the JADES collaboration team from the Scuola Normale Superiore. “It’s amazing that the universe can create such a galaxy in just 300 million years.”
JADES-GS-z14-0 provided some surprises
Not everything about JADES-GS-z14-0 was immediately clear to the JADES team, and some elements could confuse our view of the early cosmos.
When it was first spotted, the original galaxy was so close to a closer foreground galaxy that the team suspected they might be celestial neighbors. This idea was rejected last October when the JADES crew conducted a five-day in-depth analysis of JADES-GS-z14-0 with NIRCam. The application of filters specifically tailored to identifying early galaxies confirmed the extreme distance to JADES-GS-z14-0.
“We simply couldn’t see any plausible way to explain this galaxy as just a neighbor of the more nearby galaxy,” said Kevin Hainline, a JADES team member and University of Arizona researcher.
The galaxy also surprised its discoverers because its light is even redder than expected. That’s because the light from JADES-GS-z14-0 ‘turns red’ due to dust within it, which will become the building blocks of stars that will help this galaxy grow even bigger.
Another surprise was the discovery of oxygen in JADES-GS-z14-0. Elements heavier than hydrogen and helium are forged by stars during their lifetime and then spread through galaxies when these stars explode. The observation of oxygen in JADES-GS-z14-0 could indicate that at least one generation of stars already lived and died in this very early galaxy.
“Taken together, these observations tell us that JADES-GS-z14-0 does not resemble the kind of galaxies that theoretical models and computer simulations predict would exist in the very early universe,” said JADES researcher Jake Helton of Steward. Observatory and the University of Arizona said. “Given the observed brightness of the source, we can predict how it will grow over cosmic time, and so far we have not found suitable analogues of the hundreds of other galaxies we observed at high redshift in our study.”
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Helton added that given the relatively small part 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 with the JWST over the next decade, possibly even sooner,” he concluded. “We are thrilled to see the extraordinary diversity of galaxies that existed at the cosmic dawn!”