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| A sampling of thousands of galaxies of varying ages observed by the James Webb Space Telescope (Image credit: ESA/Webb, NASA & CSA, A. Martel) |
Astronomers using the James Webb Space Telescope have detected the four oldest
galaxies in the known universe, which are forming stars much faster than
thought possible.
Astronomers using the James Webb Space Telescope (JWST) have just discovered
the four most distant galaxies ever seen, located a little over 13 billion
light-years from Earth. This means astronomers are seeing what galaxies looked
like only 300 to 500 million years after the Big Bang, in the infancy of our
now almost 14 billion-year-old universe, according to two
new
studies
published April 4 in the journal Nature Astronomy.
"The frontier is moving almost every month," Pieter van Dokkum, a professor
of astronomy at Yale University who was not involved in the studies, said in
a
commentary published
in Nature Astronomy. There are now "only 300 million years of unexplored
history of the universe between these galaxies and the Big Bang," van Dokkum
added.
This may sound like familiar news, as several studies have recently claimed
possible detections of even older galaxies using JWST in the past few
months. The four newly discovered galaxies are different, though —
astronomers have actually confirmed these are ancient galaxies and not some
other celestial body, or a closer-by galaxy masquerading as a more distant
one.
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| Observations of the four oldest known galaxies in the universe, taken with the James Webb Space Telescope (Image credit: Nature Astronomy/ JWST) |
For nearby galaxies, astronomers usually use color to estimate redshift, a
parameter that describes distance as light waves stretch and turn redder while
zooming across the expanding universe. However, this technique is a dicier
choice when exploring wholly new frontiers like those being studied with JWST.
In what van Dokkum describes as a "technical tour de force," the authors of
the new research used detailed measurements of the galaxies' spectra, or the
range of light they emit over different frequencies, to double-check the
accuracy of the redshifts.
These four galaxies exist in the epoch of reionization, a time when
astronomers think the first stars were being created. Once they confirmed the
galaxies' ages, the researchers sized up the galaxies’ stars, finding that
they were quite small, at least compared with our Milky Way. But the galaxies
were also creating stars at a fast pace — something that was "surprising so
early in the universe," study co-author Stéphane Charlot, a researcher
at the Astrophysics Institute of Paris, told the
French news agency AFP.
The galaxies also don't appear to contain any particularly complex elements,
suggesting that their stars haven't yet had time to create heavier elements
and are instead made of the original hydrogen and helium atoms from the
early universe, according to the researchers.
"Galaxies had to grow up fast indeed," van Dokkum wrote, referring to the
300 million years in which these ancient galaxies formed. "To put this
length of time in perspective, sharks have been around for longer!"
When JWST launched in December 2021, astronomers hoped it would find the
first galaxies — but results like these are showing that galaxies may have
started earlier than anyone had previously thought.
"The birth of the first galaxies may have been so early that it lies beyond
even JWST's powers," van Dokkum wrote.
References:
B. E. Robertson et al, Identification and properties of intense star-forming
galaxies at redshifts z > 10, Nature Astronomy (2023).
DOI: 10.1038/s41550-023-01921-1
Emma Curtis-Lake et al, Spectroscopic confirmation of four metal-poor
galaxies at z = 10.3–13.2, Nature Astronomy (2023).
DOI: 10.1038/s41550-023-01918-w
Pieter van Dokkum, An exciting era of exploration, Nature Astronomy (2023).
DOI: 10.1038/s41550-023-01946-6
Originally published on Live Science
Tags:
Space & Astrophysics