- 4360 - JAMES WEBB - finds dark matter? - Can the James Webb telescope directly test one theory for dark matter? What is it about galaxies and dark matter? Most, if not all galaxies are surrounded by halos of this mysterious, unknown, but ubiquitous material. And, it also played a role in galaxy formation.
------------------- 4360 - JAMES WEBB - finds dark matter?
- The nature of the role of dark matter is
something astronomers are still figuring out. Today, they’re searching the
infant Universe, looking for the tiniest, brightest galaxies. That’s because
they could help tell the tale of dark matter’s role in galactic creation.
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- Simulations of early galaxy formation on
computer programs track the circumstances of galactic births not long after the
Big Bang. They take into account previously neglected interactions between dark
matter and the primordial “stuff” of the Universe, hydrogen and helium gas.
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- The result of the simulations: tiny, bright
galaxies that formed more quickly than in computer models that didn’t include
those motions. Now astronomers just need to find them, using JWST, in an effort
to see if their theories of dark matter hold up.
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- How would interactions between baryonic
matter and dark matter make a difference?
In the early Universe, clouds of gas moved at supersonic speeds past
clumps of dark matter. It bounced off the dark matter. Eventually, after
millions of years, the gaseous material fell back together to form stars in a
blast of star birth. The team’s simulations track the formation of those
galaxies right after the Big Bang.
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- The existence of smaller, brighter, more
distant galaxies could confirm the so-called “cold dark matter” model. It
suggests that the Universe was in a hot dense state containing only gases after
the Big Bang. Over time, it evolved to a lumpy distribution of galaxies (and
eventually galaxy clusters).
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- Along the way, stars and galaxies formed,
but the earliest steps likely depend on gravitational interaction with dark
matter. If the supersonic interactions
modeled actually happened, then those little galaxies would be the
result.
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- JWST has seen some early galaxies during
its time in operation. It hasn’t detected the very earliest ones—yet. However,
the images it has provided are tantalizing hints at what might exist in earlier
epochs and could provide insight into the role of dark matter.
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- The discovery of patches of small, bright
galaxies in the early universe would confirm that we are on the right track
with the cold dark matter model because only the velocity between two kinds of
matter can produce the type of galaxy.
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- JWST begins to look for galaxies that are
much brighter than expected. If they exist, that will likely prove the
interactions occurred early in cosmic time. If none can be found, then maybe
scientists still might not understand dark matter interactions. The big
question to answer is, if they exist, then how did they form so quickly and why
are they so bright?
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- The standard cosmological model says that
the gravitational pull of clumps of dark matter in the early Universe attracted
ordinary matter. Eventually, that caused stars to form, followed by galaxies.
Dark matter is thought to move more slowly than light. So, astronomers
predicted that the star- and galaxy-formation processes happened very
gradually.
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- But, what if something else was going on
more than 13 billion years ago? How would that change things? It was a time
before the first galaxies formed. But, it was a time when ordinary matter in
the form of large over densities of hydrogen and helium gas streamed through
the expanding Universe. It bounced off slower-moving clumps of dark matter and
outran its gravitational pull, at least for a time. Then, the baryonic matter
massed together again, under the influence of dark matter. That’s when the star
birth fireworks began.
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- While the streaming suppressed star
formation in the smallest galaxies, it also boosted star formation in dwarf
galaxies, causing them to outshine the non-streaming patches of the universe. The accumulated gas began to fall together
after millions of years. That led to a huge burst of star formation.
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- Lots of massive hot, young stars began to
shine, out-brilliancing the stars in other small galaxies. Ultimately what this
means is that since dark matter is impossible to “see”, those brightly shining
patches of galaxies could be indirect evidence of its existence. And, they’d
prove the role dark matter played in the creation of galaxies.
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- JWST is a perfect telescope to help see
these early galaxies. It should be able to peer into regions of the Universe
where tiny infant galaxies are brighter than astronomers expect them to be.
That extreme luminosity will help JWST spot them, showing them as they looked
at a time when the Universe was only a few hundred million years old.
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- Because dark matter is impossible to study
directly, searching for those bright patches of baby galaxies in the early
Universe could offer an effective test for theories about dark matter and its
role in shaping the first galaxies.
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February 17, 2024 JAMES
WEBB - finds dark matter? 4360
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--------------------- --- Sunday, February 18,
2024
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