- 4431 - BLACK HOLES CAME FIRST? - Black holes not only existed at the dawn of time, they birthed new stars and supercharged galaxy formation. New theories are challenging classical understanding that they formed after the first stars and galaxies emerged.
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------------------------------------ 4431 - BLACK HOLES CAME FIRST?
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- Instead, black holes might have
dramatically accelerated the birth of new stars during the first 50 million
years of the universe, a fleeting period within its 13.8 billion-year history.
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- We know these monster black holes exist at
the center of galaxies near our Milky Way, but the big surprise now is that
they were present at the beginning of the universe as well and were almost like
building blocks or seeds for early galaxies.
They really boosted everything, like gigantic amplifiers of star
formation, which is a whole turnaround of what we thought possible before, so
much so that this could completely shake up our understanding of how galaxies
form.
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- Distant galaxies from the very early
universe, observed through the Webb telescope, appear much brighter than
scientists predicted and reveal unusually high numbers of young stars and
supermassive black holes.
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- Conventional wisdom holds that black holes
formed after the collapse of supermassive stars and that galaxies formed after
the first stars lit up the dark early universe. But the analysis by Silk's team
suggests that black holes and galaxies coexisted and influenced each other's
fate during the first 100 million years. If the entire history of the universe
were a 12-month calendar, those years would be like the first days of January.
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- Black hole outflows crushed gas clouds,
turning them into stars and greatly accelerating the rate of star
formation. Otherwise, it's very hard
to understand where these bright galaxies came from because they're typically
smaller in the early universe. Why on earth should they be making stars so
rapidly?
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- Black holes are regions in space where
gravity is so strong that nothing can escape their pull, not even light.
Because of this force, they generate powerful magnetic fields that make violent
storms, ejecting turbulent plasma and ultimately acting like enormous particle
accelerators. This process is likely why Webb's detectors have spotted
more of these black holes and bright galaxies than scientists anticipated.
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- The enormous winds coming from the black
holes crush nearby gas clouds and turn them into stars. That's the missing link
that explains why these first galaxies are so much brighter than we expected.
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- During the first phase, high-speed outflows
from black holes accelerated star formation, and then, in a second phase, the
outflows slowed down. A few hundred million years after the big bang, gas
clouds collapsed because of supermassive black hole magnetic storms, and new
stars were born at a rate far exceeding that observed billions of years later
in normal galaxies. The creation of stars slowed down because these powerful
outflows transitioned into a state of energy conservation reducing the gas
available to form stars in galaxies.
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- We thought that in the beginning, galaxies
formed when a giant gas cloud collapsed.
The big surprise is that there was a seed in the middle of that cloud—a
big black hole—and that helped rapidly turn the inner part of that cloud into
stars at a rate much greater than we ever expected. And so the first galaxies
are incredibly bright.
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- The James Webb Space Telescope is probing
galaxies near the dawn of time. One of these is the exceptionally luminous
galaxy GN-z11, which existed when the universe was just a tiny fraction of its
current age. Initially detected with the NASA/ESA Hubble Space Telescope, it is
one of the youngest and most distant galaxies ever observed, and it is also one
of the most enigmatic. Why is it so bright?
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- Studying GN-z11 with Webb found the first
clear evidence that the galaxy is hosting a central, supermassive black hole
that is rapidly accreting matter. Their finding makes this the most distant
active supermassive black hole spotted to date. These were the first clear signatures that
GN-z11 is hosting a black hole that is gobbling matter.
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- They also found indications of ionized
chemical elements typically observed near accreting supermassive black holes.
Additionally, they discovered that the galaxy is expelling a very powerful
wind. Such high-velocity winds are typically driven by processes associated
with vigorously accreting supermassive black holes.
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- The NIRCam (Near-Infrared Camera) has
revealed an extended component, tracing the host galaxy, and a central, compact
source whose colors are consistent with those of an accretion disk surrounding
a black hole.
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- Together, this evidence shows that GN-z11
hosts a two-million-solar-mass, supermassive black hole in a very active phase
of consuming matter.
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- A second team used Webb's NIRSpec
(Near-Infrared Spectrograph) to find a gaseous clump of helium in the halo
surrounding GN-z11. The fact that we
don't see anything else beyond helium suggests that this clump must be fairly
pristine.
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- Finding the so far unseen Population III
stars—the first generation of stars formed almost entirely from hydrogen and
helium—is one of the most important goals of modern astrophysics. These stars
are expected to be very massive, very luminous, and very hot. Their signature
would be the presence of ionized helium and the absence of chemical elements
heavier than helium.
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- The formation of the first stars and
galaxies marks a fundamental shift in cosmic history, during which the universe
evolved from a dark and relatively simple state into the highly structured and
complex environment we see today.
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April 11, 2023 BLACK
HOLES CAME FIRST? 4431
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--------------------- --- Saturday, April 13,
2024
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