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| The James Webb Space Telescope, shown in this artist’s illustration, spotted the most distant known galaxy that suddenly stopped forming stars: NORTHRUP GRUMMAN |
New James Webb Space Telescope observations reveal that the galaxy GS-9209 had
its star-forming power abruptly "quenched" by mysterious forces after millions
of years of productivity.
The James Webb Space Telescope has spotted the earliest known galaxy to ever
be "quenched" — suddenly and mysteriously halting its star formation — and
scientists think the supermassive black hole in its center could be to blame.
The galaxy, called GS-9209, formed most of its stars during a hyperactive
burst of activity between 600 million and 800 million years after the Big
Bang. Then, more than 12.5 billion years ago, it suddenly stopped. The
researchers published the discovery Jan. 26 on the preprint server arXiv, so
it has yet to be peer-reviewed.
"The thing that's particularly surprising about this is how soon after the
Big Bang this galaxy has shut down its star formation. In the local
universe, most massive galaxies have shut down in what we think is a slow
process over billions of years," lead author Adam Carnall, an astrophysicist
at the Royal Observatory in Edinburgh, Scotland,
told Live Science. "When you go back to early times, there's not enough time for a slow
quenching process to happen, because it's not that old. For a long time it
was thought that we wouldn't find these sorts of things."
Light travels at a fixed speed through the vacuum of space, so the deeper
scientists look into the universe, the further back in time they see.
Scientists first spotted GS-9209 in the early 2000s. In the last five years,
astronomers have used ground-based telescopes to study the galaxy’s various
wavelengths of emitted light , flagging it as a galaxy that had potentially
been quenched. But the infrared wavelengths needed to gauge the galaxy's
distance are dampened by Earth's atmosphere, so scientists needed a very
powerful space telescope to study its age.
Enter the James Webb Space Telescope (JWST). The $10 billion space
observatory was designed to read the earliest chapters of the universe's
history in its faintest glimmers of light — picked up by the telescope’s
infrared sensors — after being stretched out from billions of years of
travel across the expanding fabric of space-time. Studying GS-9209 with the
JWST revealed that the distant galaxy roared into life 600 million years
after the Big Bang with an enormous burst of star formation. Over a
cosmically brief 200 million years, the galaxy served up enough piping-hot
stars to match the present-day Milky Way's 40 billion solar masses’ worth.
Then, 800 million years after the Big Bang, the ancient galaxy abruptly went
quiet.
The frenzy of star formation was a result of the rapid collapse of the giant
gas cloud that became the galaxy and the turbulent conditions of the early
universe, the researchers said. These factors combined to cause the stars to
ignite at a much faster rate, and at a higher efficiency, than in the
present-day universe.
"Typically, the galaxies we see today have had access to about five times as
much gas or more than they formed stars. This result and some others are
beginning to point now to that ratio being a bit higher in the early
universe," Carnall said. "The emerging picture is that at the highest
redshifts [the furthest back in time] galaxies are capable of forming more
of the available gas into stars."
Following this burst of activity, the researchers think GS-9209 was abruptly
shut down by a supermassive black hole lurking at its heart. These black
holes are born from the collapse of giant stars and grow by ceaselessly
gorging on gas, dust, stars and other black holes. The black hole at
GS-9209's center likely grew large enough to become a quasar. Quasars are
giant black holes with an enormous quantity of material circling their maws,
which heats up enough to push gas clouds away with blasts of light up to a
trillion times more luminous than the brightest stars.
"If you have a massive black hole and stuff is falling into it, that leads
to a lot of energy radiating out from that accretion," Carnall said. "This
is basically the only process that we think is capable of injecting enough
energy into the galaxy's gas over a short space of time to either heat it up
such that it doesn't collapse to form anymore stars, or to completely clear
the galaxy out of star-forming gas."
Now that they've made their initial observations of GS-9209, the researchers
plan to study the galaxy in more detail with the European Southern
Observatory's Extremely Large Telescope (ELT) — which is scheduled to make
its first observations in 2028.
Reference:
A.C. Carnall et al.
A massive quiescent galaxy at redshift 4.658. arXiv:2301.11413. Submitted January 26, 2023.
Tags:
Space & Astrophysics