The Webb Space Telescope reveals the birth of galaxies, and how the universe became transparent

The Webb Space Telescope reveals the birth of galaxies, and how the universe became transparent

Image from the James Webb Space Telescope. A pair of studies led by the University of California, Los Angeles, have demonstrated some of the scientific advances that the telescope enables. Credit: NASA

The oldest galaxies were cosmic fireballs that turned gas into stars at dizzying speeds across their entire extent, reports a UCLA-led study that will be published in a special issue of Galaxies. Astrophysical Journal.

The research, based on data from the James Webb Space Telescope, is the first study of the shape and structure of those galaxies. It shows that they were not like present-day galaxies in which star formation is confined to small regions, such as the constellation of Orion in our Milky Way.

We are witnessing the formation of galaxies New stars The pace is amazing,” said Tommaso Trio, lead author of the study and a professor of physics and astronomy at UCLA. “Webb’s amazing resolution allows us to study these galaxies in unprecedented detail, and we see all of this star formation that occur within the regions of these galaxies.”

Treu directs the GLASS–JWST Early Release Scientific Program, the first results of which are the subject of the journal’s own issue. Another study led by the University of California In this issue, I found that galaxies that formed shortly after the Big Bang—within less than a billion years—may have begun burning the remnants of photon-absorbing hydrogen, bringing light into the dark universe.

“Even our best telescopes really struggled to confirm distances to such distant galaxies, so we didn’t know if they made the universe transparent,” said Guido Roberts-Borsani, a UCLA postdoctoral researcher who led the study. “Webb is showing us that not only can he do the job, he can do it with amazing ease. It’s a game-changer.”

The discoveries are two of many startling discoveries made by UCLA astrophysicists who were among the first to look through Webb’s newly opened window into the past.

The Webb Space Telescope reveals the birth of galaxies, and how the universe became transparent

We show each galaxy a color composite image based on the short wavelength camera (B = F115W, G = F150W, R = F200W) and one based on the long wavelength camera (B = F277W, G = F356W, R = F444W). Individual images are degraded to the lower resolution of each camera (i.e., F200W and F444W, respectively). Postage measures 2.4 inches on its side. The pixels are 31 mA and 63 mA respectively for short and long wavelength images. Credit: T. Treu et al

Webb is the largest near-infrared telescope in space, and its remarkable resolution provides an unparalleled view of objects so distant that it takes billions of years for their light to reach Earth. Although these objects are now very old, only the light from their earliest moments has had enough time to travel the universe to end up on Webb’s detectors. As a result, not only has Webb acted as a time machine — taking scientists back to the period shortly after the Big Bang — but the images he produces have become a family album, with snapshots of newborn galaxies and stars.

GLASS-JWST was one of 13 early science projects selected by NASA in 2017 to quickly produce publicly available datasets and to demonstrate and test the tools’ capabilities on the Web.

The project seeks to understand how and when light from the first galaxies burned through the hydrogen haze left over from the Big Bang – a phenomenon and time period called the era of reionization – and how gas and heavy elements are distributed in and around galaxies over the universe. time. Treu and Roberts-Borsani are using three of Webb’s innovative near-infrared instruments to take detailed measurements of distant galaxies in the early universe.

The era of reionization is a period still poorly understood by scientists. Until now, researchers did not have the highly sensitive infrared instruments needed to observe galaxies that existed at the time. Before cosmic reionization, it was early universe It remained devoid of light because ultraviolet photons from early stars were absorbed by it hydrogen atoms that saturated space.

Scientists believe that sometime during the first billion years of the universe, radiation from the first galaxies and possibly the first black holes caused hydrogen atoms to lose electrons, or ionize, preventing photons from “sticking” to them and clearing a path for the photons to travel through space. As the galaxies began to ionize in larger and larger bubbles, the universe became transparent and light traveled freely, much as it does today, allowing us to see a dazzling canopy of stars and galaxies every night.

Roberts Borsani’s discovery that galaxies formed faster and earlier than previously thought could confirm that they were the cause of cosmic reionization. The study also confirms that the distance to two is the farthest galaxies Known using a new technique that allows astronomers to probe the beginning of cosmic reionization.

more information:
T. Treu et al., Early results from GLASS-JWST. XII: The morphology of galaxies in the era of reionization, arXiv (2022). DOI: 10.48550/arxiv.2207.13527

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