The second and fourth most distant galaxies ever seen have been spotted by the eagle eye of the James Webb Space Telescope (JWST), supporting the fundamental picture of galaxy formation as described by the Big Bang theory.
The invention was made possible due to an enormous helping hand from a large gravitational lens in the shape of the galaxy cluster generally known as Abell 2744, nicknamed Pandora’s Cluster, which is situated about 3.5 billion light years away from us. The immense gravity of the cluster warps the very fabric of space-time sufficiently to magnify the sunshine of more faraway galaxies.
Using the James Webb Space Telescope to go looking for early galaxies magnified by this cosmic lens, Bingjie Wang of the Penn State Eberly College of Science and member of the JWST UNCOVER (Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization) team discovered two of the very best redshift galaxies ever seen.
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Cosmological redshift is the stretching of sunshine wavelengths, provoked by the continual expansion of the universe. The more distant a galaxy is, the more the universe had expanded while that galaxy’s light traveled across space to succeed in us, and subsequently, the more the wavelengths of that light are stretched. As wavelengths get stretched out in this way, they go from tighter, blueish ones to redder ones, eventually falling into the invisible, infrared region of the electromagnetic spectrum. Galaxies that existed just between 300 and 400 million years after the Big Bang have had their light stretched into those infrared wavelengths that cannot be seen by humans, but can indeed be detected by the JWST’s Near-Infrared Camera (NIRCam) and Near-Infrared Spectrometer (NIRSPec).
Wang and her team were in a position to discover the lensed images of two high-redshift galaxies. One, designated UNCOVER-z13 (“z” is shorthand for “redshift”), has a redshift of 13.079, confirming it to be the second most distant galaxy known. (Essentially the most distant confirmed galaxy is JADES-GS-z13-0, which was also discovered by the JWST in 2022 and has a redshift of 13.2.) We see UNCOVER-z13 because it existed just 330 million years after the Big Bang.
The opposite galaxy recently discovered, UNCOVER-z12, has a redshift of 12.393, placing it in fourth place within the all-time list of most distant galaxies. We see this realm because it was just 350 million years after the Big Bang.
What marks the 2 UNCOVER galaxies out as different is their appearance. Other galaxies seen at similarly high redshifts appear to be point-like, indicating they’re very small — just just a few tons of of sunshine years across. The UNCOVER galaxies, however, have structure.
“Previously discovered galaxies at these distances … appear as a dot in our images,” Wang said in a statement. “But one in all ours appears elongated, almost like a peanut, and the opposite looks like a fluffy ball.”
These galaxies are also greater, with UNCOVER-z12 sporting an edge-on disk about 2,000 light years across, which is six times larger than other galaxies seen on this era.
“It’s unclear if the difference in size is attributable to how the celebrities formed or what happened to them after they formed, but the range within the galaxy properties is de facto interesting,” said Wang. “These early galaxies are expected to have formed out of comparable materials, but already they’re showing signs of being very different than each other.”
Although the dichotomy in galaxy properties, even at this early stage within the universe, is eye-opening, each of the newfound realms have general characteristics which can be strongly supportive of the Big Bang model. This model describes how, within the aftermath of our universe’s creation, galaxies began life small before growing rapidly through mergers with other galaxies and gas clouds. This growth, in turn, spurred more star formation, which ultimately increased the abundance and number of elements contained inside the young galaxies, introducing substances to them which can be heavier than hydrogen and helium. The galaxies uncovered by UNCOVER — for those who’ll pardon the pun — are young, small, have a low abundance of heavy elements and are actively forming stars, all of which supports “the entire paradigm of the Big Bang theory,” Joel Leja, who’s an assistant professor of astronomy and astrophysics at Penn State University and a co-researcher on Wang’s team, said within the statement.
Interestingly, the JWST has the power to see even higher redshift galaxies than UNCOVER-z13 and -z12, meaning they’d be even younger — nevertheless it didn’t detect any being lensed by the Pandora Cluster. “That might mean that galaxies just didn’t form before that point and that we’re not going to search out anything farther away,” said Leja. “Or it could mean we didn’t get lucky enough with our small window.”
Astronomers will keep looking, using a mess of lensing clusters to open up recent windows into the deep universe in quest of a number of the first galaxies.
The invention was reported on Monday (Nov. 13) in Astrophysical Journal Letters.