by The James Webb Space Telescope (JWST) has found not one but two of the earliest and most distant galaxies ever seen, 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, at least 100 million years earlier than the previous record holder. That means the light seen by the JWST from this primordial galaxy has been traveling for 13.5 billion years on its way to reach us.
JADES-GS-z14-0 is not alone, either. It was discovered along with another galaxy, JADES-GS-z14-1, which is almost as far away and takes second place in the ranking of the earliest galaxies ever seen by mankind.
Related: The James Webb Space Telescope shows 3 of the universe’s earliest galaxies
The announcement of the discoveries, made in October 2023 and January 2024, are the latest developments in the ongoing investigation of cosmic dawn facilitated by the $10 billion telescope as part of JWST’s Advanced Deep Extragalactic Survey (JADES) program. JADES aims to provide critical insights into the ways in which stars, gas, and black holes formed in primordial galaxies when the universe was 13.8 billion years old.
“These galaxies contribute to a small but growing population of galaxies from the first half billion years of cosmic history where we can probe the stellar populations and the specific patterns of chemical elements within them,” Kavli Institute of Cosmology staff member and scientist Francesco D’ Eugenio said in a statement.
JADES-GS-z14-0 isn’t just remarkable for how far it is from Earth and how early it’s been in the cosmos, though. With a width of about 1,600 light-years across, this “cosmic beauty” galaxy is also notable for its size and brightness.
“The size of the galaxy clearly proves that most of the light is being produced by a large number of young stars, rather than material falling into a supermassive black hole at the center of the galaxy, which [make it] appear much smaller,” said JADES team leader Daniel Eisenstein of the Harvard & Smithsonian Center for Astrophysics (CfA) in a separate statement.
The extreme brightness of JADES-GS-z14-0 and the fact that this luminosity is powered by young stars means that this galaxy is the most striking evidence of the rapid formation of large, massive galaxies in the early universe found so far.
JADES team member and University of California-Santa Cruz researcher Ben Johnson said that JADES-GS-z14-0 shows that the formation of galaxies in the early universe was very fast and intense.
“The JWST will enable us to find more of the galaxies, perhaps when the universe was still younger,” he said. “It’s a great opportunity to study how galaxies get started.”
The James Webb Space Telescope sees red to see early galaxies
The JWST is able to see early galaxies because of the high infrared sensitivity of its instruments, especially its main imager, the Near Infrared Camera (NIRCam).
Light from these cosmic speckled galaxies leaves a wide range of wavelengths 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 is expanding, and as light passes through, its wavelength is stretched 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 further away have to cross more space (which is being stretched as it expands) before their light reaches us, and therefore, that light travels more perspectives. Redshift, denoted as z, can therefore be used to measure the distance to celestial objects with known spectra. 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 gradual change z = 14.32, and the most distant galaxy before it, JADES-GS-z13-0, has retransitioned z = 13.2, which placed it 400 million years after the Big Bang. This newly discovered galaxy has clearly broken that record, with the JWST coming back in time by another 100 million years or so.
“JADES-GS-z14-0 is now the epitome of this phenomenon,” said Stefano Carniani, member of the JADES collaboration team, from the Scuola Normale Superiore. “It’s amazing that the universe can’t make such a galaxy in 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 several aspects could confuse our picture of the early cosmos.
When it was first observed, the primordial galaxy was so close to a closer foreground galaxy that the team suspected they might be celestial neighbors. This idea was put to rest in October last year when the JADES crew spent five days doing an in-depth analysis of JADES-GS-z14-0 with NIRCam. Application of filters specifically tailored to identify early galaxies confirmed the large distance to JADES-GS-z14-0.
“We couldn’t see any plausible way to explain this galaxy because it’s just a closer neighbor of the galaxy,” said JADES team member and University of Arizona researcher Kevin Hainline.
The galaxy also surprised its discoverers because its light is redder than expected. That’s because the light from JADES-GS-z14-0 is being “reddened” by dust inside it which will be 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. Stars create elements heavier than hydrogen and helium during their lifetime and then distribute them through galaxies when these stars explode. The observation of oxygen in JADES-GS-z14-0 may indicate that at least one generation of stars lived and died in this very early galaxy.
“All these observations, together, tell us that JADES-GS-z14-0 is not like the types of galaxies predicted by theoretical models and computer simulations to exist in the early universe,” JADES researcher Jake Helton of Steward said the Observatory and the University of Arizona. “Given the observed brightness of the source, we can predict how it might grow over cosmic time, and so far, we have not found any suitable analogues from the hundreds of other galaxies we have observed at high redshift in our survey. “
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Helton added that given the relatively small region of the sky the JWST searched to find JADES-GS-z14-0, its discovery has major implications for the projected number of bright galaxies we see in the early universe.
“Astronomers are likely to find many such luminous galaxies, perhaps at even earlier times, over the next decade with the JWST,” he said. “We are thrilled to see the amazing variety of galaxies that existed at the cosmic dawn!”
