This month, researchers announced the results from one of the largest and deepest astronomical surveys of the night sky ever conducted by the James Webb Space Telescope (JWST). The effort identified some of the earliest galaxies ever seen — from within the first 650 million years after the Universe was born in the Big Bang. And the findings dazzle astronomers, showing that stars and galaxies form and evolve much earlier than anyone suspected.
JWST sees 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, which revealed thousands of galaxies. Unlike Hubble, however, JWST operates primarily on infrared wavelengths of light, making it ideal for seeing very distant galaxies, the light from which has been stretched as the Universe expands, making it more red
The starlight from these objects traveled such great distances that they appeared not long after the Big Bang occurred, 13.8 billion years ago. Astronomers measure distance using a factor known as redshift: the higher the redshift, the further away the object.
Before the JWST launch in 2021, only a few dozen galaxies were detected at redshifts greater than 8. JADES identified a whopping 717 galaxies likely to be in this range.1. Here, astronomers help Nature make sense of the data deluge by choosing some of their favorite galaxies (listed from farthest to smallest) and explaining what the objects can teach us about the early days of the Universe.
The record holder
This faint red blob may not look like much, but it is the current record holder for the most distant object known in the Universe. JWST discovered the galaxy, known as JADES-GS-z13-0, last year and later confirmed2, through detailed studies of its star’s luminosity, that it is at a redshift of 13.2. This means that it appears to be only 320 million years after the Big Bang.
The galaxy is physically small, only a few hundred light years across, but is churning out new stars at a rate comparable to today’s Milky Way, said Brant Robertson, an astronomer at the University of California, Santa Cruz. That’s remarkable because scientists thought the first galaxies to form in the Universe would slowly coalesce as stars burned and merged. Showing JADES-GS-z13-0 and other items3 that the first galaxies were hotbeds of star formation.
“These galaxies are the building blocks of structure in the Universe,” said Kevin Hainline, an astronomer at the University of Arizona in Tucson. At JWST, he added, “we see them everywhere”.
The glowing dog bone
Researchers think this dog-bone-shaped object is at redshift 11.3, although that distance still needs to be confirmed. Assuming it is, then it appears to be about 400 million years after the Big Bang.
JWST finds more structure in the early Universe than anyone expected: the dog bone appears to be two smaller galaxies in the process of merging. So, by 400 million years after the Big Bang, the Universe had already formed stars that clustered into galaxies, and two of those galaxies had collided.
Before JWST began surveying the night sky, scientists didn’t think so much galactic action was possible this early in the Universe. “I didn’t expect to see these kinds of things in our data,” Hainline said.
The one with (maybe) the first stars
At a redshift of 10.6, this galaxy is surprisingly bright just 430 million years after the Big Bang, Robertson said. First spotted by Hubble, the galaxy, called GN-z11, appears as an incredibly compact bright sphere under JWST’s gaze4. That glow may come from a giant black hole at its center, where superheated gas and dust spiral5.
Other JWST observations suggest that this galaxy contains some of the first stars to form in the Universe6. The evidence, in the form of unusual chemical pockets of primordial helium gas around the edges of the galaxy, is tentative.
But the earliest stars were made mostly of hydrogen and helium, with very few other chemical elements. That’s exactly what JWST may have seen in GN-z11. If so, it will fulfill the long-held dream of astronomers to see these stars.
The big cluster
This bulbous galaxy is at redshift 8, where it is about 300 million years older than the record holder. Because of the clumpy structure it developed, however, those 300 million years should be action-packed.
If the 13.8 billion years of the Universe’s history were compressed into a two-hour movie, the first five minutes – which set up the framework for everything that follows – would reveal all the first galaxies that JWST is looking for. , Hainline said. And this massive galaxy, spanning about 3.7 kiloparsec (12,000 light years), indicates that the Universe was dynamic from the beginning.
This small galaxy, seen as it was 700 million years after the Big Bang, has more stars forming on its outskirts than in its center.
“This is the first time we can measure internal growth at such an early stage” of the Universe, said Sandro Tacchella, an astrophysicist at the University of Cambridge, UK. That’s surprising because theory suggests the opposite – that the first galaxies should have had stars forming closer to their centers.
This galaxy appears to have started almost immediately, forming as many stars in its compact heart as the massive galaxies of today.7. After that, it made stars out of it, which is the stage at which astronomers can see it today.
The cosmic rose
This flower-like gathering of very dusty, very red galaxies immediately caught the eye of the JADES team, earning the nickname the cosmic rose.
“It has a special place in the team’s heart,” said Stacey Alberts, an astronomer at the University of Arizona in Tucson. “Scientifically, this is a great demonstration of JWST’s leap in understanding how red the Universe is.”
The rose galaxies are probably not physically related to each other, as they are at different distances spanning redshifts from 2.5 to 3.9. But those values put them in the middle of the ‘cosmic noon’, a period around three billion years after the Big Bang, when galaxies formed stars so fast and furiously that they made most of the stars known in the Universe today.
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