Discoveries from the James Webb Space Telescope are pouring in, with an
analysis of the latest data revealing a galaxy that dates back to just 300
million years after the big bang – the oldest we have ever seen.
Just weeks into its mission, the James Webb Space Telescope (JWST) has
broken the record for the oldest galaxy ever observed by nearly 100 million
years.
Seeing some of the first galaxies to form after the big bang 13.8 billion
years ago is one of the key goals of the JWST. When these emerged is
currently unknown: the previous oldest identified galaxy, found by the
Hubble Space Telescope, is called GN-z11 and dates back to 400 million years
after the birth of the universe.
Rohan Naidu at the Harvard-Smithsonian Center for Astrophysics and his
colleagues think they have already found an older one in a publicly released
JWST data set called GLASS. Known as GLASS-z13, the galaxy dates back to
just 300 million years after the big bang. The team also found a second
galaxy, GLASS-z11, of a comparable age to GN-z11.
“We found two very compelling candidates for extremely distant galaxies,”
says Naidu. “If these galaxies are at the distance we think they are, the
universe is only a few hundred million years old at that point.”
The two galaxies appear to have already grown the equivalent mass of a
billion suns since they started forming. That is something we would expect
for galaxies that have been forming for around 500 million years, says the
team, possibly hinting that stars formed more rapidly than we thought in the
early universe. The closer galaxy, GLASS-z11, also appears to have started
to form a disc-like structure caused by its rotation.
Both galaxies are very small, GLASS-z13 being only about 1600 light years
across and GLASS z-11 about 2300 light years. By comparison, our Milky Way
is some 100,000 light years across.
Gabriel Brammer at the Niehls Bohr Institute in Denmark, part of the GLASS
team and a co-discoverer of GN-z11, says that further analysis will be
needed to confirm the distance to the two galaxies. Only JWST can do that
work. “They’re very convincing candidates,” he says. “We were pretty
confident that JWST would see distant galaxies. But we’re a little bit
surprised how easy it is to detect them.”
JWST’s immense power should make discoveries like this a regularity. Longer
hunts for ancient galaxies should be able to probe much further, perhaps to
less than 200 million years after the big bang, when some of the first
galaxies and stars in the universe are thought to have formed.
“How early does star formation start in the universe?” says Naidu. “It’s one
of the last major unknowns in our broad timeline of the universe.”
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Space & Astrophysics