This month, researchers revealed the results of one of the largest and deepest astronomical surveys of the night sky ever conducted by the James Webb Space Telescope (JWST). This effort identified some of the oldest galaxies ever seen — within the first 650 million years after the birth of the universe in the Big Bang. The results dazzled astronomers, revealing that stars and galaxies were forming and evolving much earlier than anyone expected.
JWST discovers some of the most distant galaxies ever seen
The project, known as the JWST Advanced Deep Extragalactic Survey (JADES), peered at several patches of sky, including one in the constellation Fornax — which became famous in 2004 after the Hubble Space Telescope stared at it for 11 days, revealing thousands of galaxies. Unlike Hubble, the JWST operates primarily at infrared wavelengths of light, which makes it ideal for spotting extremely distant galaxies, the light from which stretches as the universe expands, making it appear redder.
The starlight from these objects has traveled such great distances that it appeared as if it wasn’t long after the Big Bang, 13.8 billion years ago. Astronomers measure distance using a factor known as the redshift: the greater the redshift, the farther away an object is.
Prior to the launch of JWST in 2021, only a few dozen galaxies were observed at redshifts greater than 8. JADES has identified a whopping 717 galaxies that may be in this range.1. Here, astronomers help nature Make sense of the data deluge by picking some of their favorite galaxies (listed from farthest to least) and explaining what the objects can teach us about the early days of the universe.
This faint red blob may not look like much, but it is the current record holder for the farthest known object in the universe. JWST discovered the galaxy, known as JADES-GS-z13-0, late last year and then confirmed2, through detailed studies of starlight, that it is located at a redshift of 13.2. This means that it looks like it happened only 320 million years after the Big Bang.
The galaxy is physically small, a few hundred light-years in diameter, but it’s pumping out new stars at a rate comparable to today’s Milky Way, says Brant Robertson, an astronomer at the University of California, Santa Cruz. This is remarkable because scientists believed that the first galaxies that formed in the universe would slowly come together as the stars flared up and united. JADES-GS-z13-0 and other things like that appear3 that early galaxies were hotbeds of star formation.
“These galaxies are the building blocks of structure in the universe,” says Kevin Heinlein, an astronomer at the University of Arizona in Tucson. With JWST, he adds, “we see them everywhere.”
Glowing dog bone
Researchers believe this dog-bone-shaped object is at a redshift of 11.3, though this distance still needs to be confirmed. Assuming that, it looks the same as it was about 400 million years after the Big Bang.
JWST detected more structure earlier in the universe than anyone expected: the dog bones appear to be two smaller galaxies in the process of coalescing. So, by 400 million years after the Big Bang, the universe had already formed stars that had coalesced into galaxies, and two of those galaxies had come together.
Before the James Webb Space Telescope began surveying the night sky, little did scientists think that this much galactic motion was possible so early in the universe. “I wasn’t expecting to see these types of objects at all in our data,” Hainline says.
The one who has (maybe) the first stars
At a redshift of 10.6, this galaxy appears surprisingly bright just 430 million years after the Big Bang, Robertson says. The galaxy called GN-z11, first spotted by Hubble, has appeared as an incredibly compact ball under JWST’s gaze.4. This brightness may come from a supermassive black hole at its center, around which shielded gas and dust spirals spirally5.
Other JWST observations indicate that this galaxy contains some of the first stars formed in the universe6. The evidence, in the form of chemically unusual pockets of primordial helium gas around the edges of the galaxy, is tentative.
But the first stars were composed mostly of hydrogen and helium, with very few other chemical elements. This is exactly what JWST may have spotted on the GN-z11. If so, it will fulfill astronomers’ long-held dream of discovering these stars.
A big lumpy one
This bulging galaxy is located at a redshift of 8, which puts it about 300 million years behind the record holder. However, due to the lumpy structure it had developed, those 300 million years must have been full of excitement.
If the universe’s 13.8 billion years of history were compressed into a two-hour movie, Hainline says, the first five minutes — which plot all that follows — would feature all of the early galaxies detected by the JWST. And this massive galaxy, which spans about 3.7 kilofarcis (12,000 light-years) across, indicates that the universe was dynamic from the beginning.
From the inside out
This small galaxy, seen 700 million years after the Big Bang, has more stars forming in its outskirts than in its center.
“It’s the first time we can measure the internal growth at such an early stage” of the universe, says Sandro Taquila, an astrophysicist at the University of Cambridge, UK. This is surprising because the theory suggests the opposite — that early galaxies must have had stars forming near their centers.
This galaxy seems to have started right away, forming as many stars in its compact core as the larger galaxies do now7. After that, it turned to making stars at its fringes, which is the stage at which astronomers can see it today.
This flower-like grouping of very dusty, extremely red galaxies caught the JADES team’s attention almost immediately, earning it the nickname the Cosmic Rose.
“He holds a special place at the heart of the team,” says Stacy Alberts, an astronomer at the University of Arizona in Tucson. “Scientifically, it’s a beautiful demonstration of JWST’s leap forward in understanding how red the universe is.”
The Rosette galaxies are probably not physically related to each other, as they lie at varying distances that include redshifts of 2.5 to 3.9. But those values put it at the heart of “cosmic noon,” a period about three billion years after the Big Bang, when galaxies formed stars so rapidly and vigorously that they produced most of the stars known in the universe today.
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