The James Webb Space Telescope (JWST) is a space telescope primarily developed for infrared astronomy. As the largest optical telescope in orbit, its excellent infrared resolution and sensitivity allow it to see objects that the Hubble Space Telescope cannot see because they are too early, far, or dim. This is planned to enable a wide range of astronomical and cosmological inquiries, such as the detection of the earliest stars and the development of the first galaxies, as well as thorough atmospheric characterization of possibly habitable exoplanets.
Webb’s photographs show a plethora of galaxies gleaming in the distant cosmos, appearing just a few hundred million years after the Big Bang, 13.8 billion years ago. Astronomers’ beliefs about the early Universe have been challenged by the telescope’s extraordinarily crisp images.
“We had in mind an idea of what galaxies at these [distances] would look like, and how much detail we’d be able to see, but I think the reality is just kind of blowing our mind,” says Jeyhan Kartaltepe, an astronomer at the Rochester Institute of Technology in New York.
Here are some of the things astronomers have learned from Webb’s initial observations
There are an awful lot of galaxies way out there
Because Webb detects infrared light and because the cosmos’ expansion stretches light to redder wavelengths, it is best adapted to detecting galaxies that formed early in the Universe’s history. Webb detected several distant galaxies that are beyond the reach of other observatories, like as the Hubble Space Telescope, in its initial observation program, which began in June.
The age of early galaxies began roughly 250 million years after the Big Bang, when the first stars emerged and illuminated the Universe. Later generations of stars grew into galaxies, which are the dim red blobs that Webb is now discovering. Many of the Webb photos contain previously unseen galaxies in the distant Universe. “There’s almost no free space where there isn’t stuff,” Kartaltepe explains.
One study went through data from many of Webb’s distant galaxy fields to determine the pace at which stars created in the early Universe. It discovered 44 previously unknown galaxies dating back to 300 million years after the Big Bang. The observations, when combined with 11 previously known galaxies, suggest that there was a huge population of galaxies generating stars in the early Universe1. The findings “re-affirm the great promise of incoming larger [Webb] programmes to alter our understanding of the young Universe,” wrote the researchers, lead by Callum Donnan of the University of Edinburgh in a report published on the arXiv preprint server.
Many galaxies are competing for the ‘most distant’ title
The stampede of research teams racing to discover the most distant galaxy in the Webb data is perhaps the most visible rush. A number of contenders have been identified that will need to be confirmed by additional research, but all of them would break Hubble’s record for the most distant galaxy, which dates back to about 400 million years after the Big Bang.
One contender surfaced in a Webb scan dubbed GLASS, which also included another, somewhat less distant galaxy. “The discovery of these two brilliant galaxies was a real surprise,” says Marco Castellano, an astronomer at Rome’s National Institute for Astrophysics. He and his colleagues had not expected to find such distant galaxies in such a small area of the sky. A second team discovered the two galaxies independently.
Some early galaxies are surprisingly complex
Webb’s distant galaxies are also revealing more complexity than astronomers predicted. One investigation of Webb’s first deep-field image discovered an unexpectedly large number of distant galaxies with disk-like shapes9. Using Hubble, astronomers discovered that distant galaxies are more irregularly shaped than nearer galaxies, which, like the Milky Way, have uniform shapes like discs. According to the notion, early galaxies were more frequently warped by interactions with neighboring galaxies. The Webb data, on the other hand, show that there are up to ten times as many distant disk-shaped galaxies as previously thought.
Another preprint manuscript contends that huge galaxies arose earlier in the history of the Universe than previously thought. A team lead by Ivo Labbé of Swinburne University of Technology in Melbourne, Australia, reports finding seven large galaxies with redshifts ranging from 7 to 10. The scientists write, “We infer that the central areas of at least some huge galaxies were already largely in place 500 million years after the Big Bang, and that massive galaxy formation began extremely early in the history of the Universe.”
Closer galaxies are smaller than expected
Webb’s surprises continue much later in the Universe’s evolution. One study looked at Webb’s findings of ‘cosmic noon,’ which occurred about three billion years after the Big Bang. This is when the Universe’s star creation peaked and the most light was produced. Wren Suess, an astronomer at the University of California, Santa Cruz, examined Hubble and Webb photographs of galaxies around cosmic noon. Most of the big galaxies seemed substantially smaller in Webb’s infrared wavelengths than they did in Hubble images12. “It has the potential to revolutionize our entire understanding of how galaxy sizes evolve over time,” Suess says. Hubble investigations revealed that galaxies begin small and grow larger over time, but the Webb discoveries suggest that Hubble did not have the complete picture and that galactic evolution may be more intricate than astronomers thought.
