Webb telescope turns up baffling views of the early universe
Just over a year after its historic launch, NASA’s James Webb Space Telescope (JWST) is challenging astronomers’ expectations of the early universe and showing that massive galaxies likely formed much earlier than predicted.
JWST sees in the far infrared part of the electromagnetic spectrum that is invisible to our eyes, according to NASA. This means that the telescope is optimized to capture light from the early universe, which has stretched towards these longer, redder wavelengths as the universe has expanded over time – a process known as redshift.
Galaxies can come in many different types, including beautiful spiral galaxies like our Milky Way, as well as elliptical or irregular types, astronomer Jeyhan Kartaltepe of the Rochester Institute of Technology in New York said during a press conference at the 241 meeting of the American Astronomical Society in Seattle, Washington.
The Hubble Space Telescope had already seen all the different types of galaxies as far back as 11 billion years ago, suggesting their formation took place even earlier, she added. Some researchers thought JWST could finally see these early stages of galaxy formation because the telescope sees further into cosmic history than Hubble, Kartaltepe said.
She and her team analyzed 850 galaxies between 11 and 13 billion years ago, classifying them according to whether they were spiral, elliptical, irregular or some combination of the three. They found that the percentage of each galaxy type remained roughly the same as in the modern universe throughout that time period.
This shows that the galaxies were already quite mature even at this stage of cosmic history, said Kartaltepe. “We’re not seeing the earliest formation of galaxies yet,” she added. Her team’s findings have been accepted for publication in the Astrophysical Journal, according to the Rochester Institute of Technology.
The oldest galaxies in the universe?
A pair of color composite images of the galaxy cluster SMACS 0723-27 and its surroundings, taken by NASA’s James Webb Space Telescope. The galaxies involved may be the earliest known galaxies in the universe – some 200-400 million years after the Big Bang. (Image credit: Haojing Yan, Bangzheng Sun, NASA, European Space Agency, Canadian Space Agency and Space Telescope Science Institute)
Another strange view of the early universe came from University of Missouri astronomer Haojing Yan. He and his colleagues looked at one of the first JWST pictures — a field of stars, galaxies and galaxy clusters known as SMACS 0723 — and noted some of the oldest galaxies ever observed.
Yan’s team identified 87 galaxies in this field that may have been present only 200 to 400 million years after the big bang, an unusually early age to see so many galaxies. Further analysis will be needed to confirm that these primordial galaxies are actually located at such early times, but Yan said he would “bet $20 and a beer” that at least half would end up being correctly located within days. such ancient ones.
While many researchers thought JWST would find at least a handful of galaxies so far in cosmic history, few expected it to turn up so many, Yan added. “Even if only a small fraction turns out to be true,” he said, “then our previously favored picture of galaxy formation in the early universe needs to be revised.”
Yan declined to speculate on what might have caused galaxies to form much earlier than predicted in the universe, but he said it is now up to theorists to come up with plausible explanations for such observations. His team’s work appeared in the Astrophysical Journal in December.
‘Green peas’ since the dawn of time
A trio of faint objects (circled) captured in the James Webb Space Telescope’s Deep Image of the galaxy cluster SMACS 0723 exhibit properties strikingly similar to rare, small galaxies called “green peas” found much closer home. (Image credit: NASA, ESA, CSA and STScI)
Astrophysicist James Rhoads of NASA’s Goddard Space Flight Center in Greenbelt, Maryland offered a recent look at the early universe during the AAS press conference. Also analyzing JWST’s SMACS 0723 deep-field image, he and his colleagues identified three small galaxies whose chemical compositions closely match a rare type of galaxy called a “green pea.”
First discovered by citizen scientists working in collaboration with the Galaxy Zoo in 2009, pea galaxies are very small – roughly 5,000 light-years across, or just one 20th the size of the Milky Way – and are home to a great deal of star formation. Rhoads said.
Green peas are rare, making up only 0.1% of all nearby galaxies, and are very pristine, according to NASA. As stars burn hydrogen and helium, they form heavier elements like oxygen and carbon, and in their death throes they throw such elements across a galaxy. But the green peas have very low levels of heavier elements, containing roughly one-fifth the oxygen of the Milky Way, similar to the three JWST-polluted objects.
“We found what may be the most chemically primitive galaxies,” Rhoads said during the press conference, adding that astronomers can use their modern counterparts to study these ancient galaxies and learn more about the early universe. The findings appeared Jan. 3 in the Astrophysical Journal Letters.
Rhoads suggested that modern green pea galaxies may be “a bit like living fossils of early galaxy formation. Coelacanths, if you will,” referring to a type of fish that was once thought to be extinct until it was found off the coast of South Africa in 1938.