The James Webb Space Telescope (JWST) has caught a glimpse of the oldest galaxies ever observed.
Astronomers are now convinced that light from these galaxy has been traveling to Earth for 13.4 billion years, two new studies report. The results show that these galaxies were inhabited the universe when it was less than 350 million years old and exhibited the rapid emergence of the first generation of galaxies.
“It was very important to prove that these galaxies do, in fact, inhabit the early universe. It’s very possible for nearby galaxies to masquerade as very distant galaxies,” said Emma Curtis-Lake, a co-author of the new study and an astronomer at the University of Hertfordshire in England. statement (opens in new tab).
“Seeing the spectra unfold as we expected, confirms that these galaxies are at the true edge of our view, some distance from it. Hubble I could see! This is an incredibly exciting achievement for the mission,” said Curtis-Lake.
Related: The James Webb Space Telescope: What you need to know
The discovery confirms JWST’s ability to perform one of its most important tasks – the study of the early universe through light that has been traveling for so long that the expansion of the universe has stretched its wavelength. This diffusion of light is called redshift; As light travels further, the expansion of the universe toward the red end of the electromagnetic spectrum diverts its light. This means that redshift can be used as a measure of distance, and should the light of early galaxies exhibit extreme redshift, their light should extend into the infrared range — JWST’s specialty.
So far, the $10 billion observatory has identified several very high-redshift candidate galaxies, but these observations must be confirmed using spectroscopy.
Spectroscopy can be used to distinguish between early galaxies and nearby, more contemporary galaxies that may share similar properties, as spectra can detect characteristic fingerprints of specific components. Early galaxies are composed mostly of hydrogen and helium, lacking heavier elements such as oxygen, nitrogen, and carbon. This is because they have not yet been enriched by the heavy elements that have been created they are Through nuclear fusion and then dispersal as these stars die and go away Supernova.
The researchers’ analysis of data collected from JWST’s near-infrared camera (NIRCam) and near-infrared spectrograph (NIRSpec) instruments allowed them to determine that the four galaxies JADES-GS-z10–0, JADES-GS-z11–0, JADES-GS -z12–0, and JADES-GS-z13–0 actually have extreme redshifts between 10.3 and 13.2. (JADES, by the way, stands for “JWST Advanced Deep Extragalactic Survey”.)
They came to this conclusion because the spectra of these galaxies lack the telltale signature of heavy elements like carbon, meaning JWST is seeing them as they did when the universe was only 300 to 500 million years old. (The universe is currently about 13.8 billion years old.)
“For the first time, we’ve discovered galaxies just 350 million years after the Big Bang, and we can be completely confident about their great distances,” co-author and NIRCam science team member Brant Robertson said in the statement. “Finding these early galaxies in such stunningly beautiful images is a special experience.”
The observations come from the first round of JADES observations, directed at a small region of the sky known as the Ultra Deep Field that has been probed by the Hubble Space Telescope for nearly two decades. This patch of sky contains about 100,000 galaxies, each captured at some point in its history, potentially billions of years into the past.
The researchers used over 10 days of the JWST mission to study the Ultra Deep Field with NIRCam, observing it in nine different infrared colors. This was followed by 28 hours of data collection conducted over three days by the NIRSpec instrument. JWST therefore provided exceptionally sensitive and sharp images of the region and provided the data astronomers needed to obtain a precise measure of the redshift of each galaxy and to reveal the properties of the gas and stars within each.
“These results are the culmination of why the NIRCam and NIRSpec teams came together to run this monitoring program,” said Marcia Raike, NIRCam principal investigator at the University of Arizona.
Both papers were published today (April 4). Journal Nature (opens in new tab). The researchers first reported the findings in December 2022, when they presented them at a conference.
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