- 4377 - UNIVERSE - clumpiness of galaxies? Using data from the James Webb Space Telescope, astronomers discovered a massive, gassy cosmic webb tendril composed of 10 closely packed galaxies stretching over 3 million light-years. This ancient filament of gas and stars may represent the oldest known thread of the cosmic web.
------------------- 4377 - UNIVERSE - clumpiness of galaxies?
- On a clear night, it might look like the
stars above are distributed more or less evenly. But that isn't the case. All stars are part of a gigantic cosmic web
that links galaxies across the universe like threads of spider's silk, leaving
unfathomably large swaths of nothingness in between.
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- This newly discovered filament formed when
the universe was young, 830 million years after the Big Bang. It is anchored by
an extremely bright celestial object with a supermassive black hole known as a
quasar at its center.
-
- This is one of the earliest filament
structures that anyone has ever found associated with a distant quasar. The black holes helped to form the cosmic
web by acting as gravity wells to draw matter together, and occasionally by
flinging it far away on "cosmic winds," which whip up around
extremely active quasars. Gravity keeps these strands of stars and dust
connected, even as the winds pull them across the universe.
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- Eventually the filament will condense into
a cluster of galaxies, similar to the Coma Cluster, which lies approximately
330 million light-years from Earth.
“Dwarf galaxies” packed enough punch to reshape the entire early
universe. The main surprise is that
these small faint galaxies had so much power, their cumulative radiation could
transform the entire universe.
-
- Astronomers have used the James Webb Space
Telescope (JWST) to see an effect predicted by Albert Einstein over 100 years
ago and to discover that small galaxies in the early cosmos packed a massive
punch, shaping the entire universe when it was less than 1 billion years old.
-
- The galaxies, which resemble dwarf galaxies
that exist today, played a vital role during a crucial stage of cosmic
evolution that occurred between 500 and 900 million years after the Big Bang.
These small galaxies also vastly outnumbered larger galaxies in the infant
universe, adding that it's likely the realms supplied most of the energy needed
for a process called cosmic reionization. 'Cosmic reionization” was critical to
the growth and progression of the universe.
-
- Prior to around 380 million years after the
Big Bang happened, during a period called the 'epoch of recombination”, the now
13.8 billion-year-old universe had been opaque and dark. This was because, in
its dense and ultra-hot state, free electrons endlessly bounced around
particles of light, called photons.
-
- Later, during the “epoch of recombination”
the universe had expanded and cooled enough to allow electrons to bond with
protons and create the first atoms of hydrogen, the lightest and simplest
element in the universe.
-
- This disappearance of free electrons meant
photons were suddenly free to travel, and as a result, the "dark age"
of the universe ended. The cosmos suddenly became transparent to light. This
"first light" can seen today in the form of a cosmic fossil that
uniformly fills the universe called the "cosmic microwave background"
or "CMB."
-
- Because electrons and protons have equal
but opposite electric charges, these first atoms were electrically neutral, but
they would soon undergo yet another trans-formation. After 400 million years, the first stars
and galaxies formed. During this “era
of reionization”, neutral hydrogen, the predominant element in the universe,
was transformed into charged particles. These particles are called “ions”.
Ionization is caused by electrons absorbing photons and increasing their
energy, breaking free from atoms.
-
- Incomprehensible as it sound, inflation
poses that the universe initially expanded far faster than the speed of light
and grew from a subatomic size to a golf-ball size almost instantaneously.
-
- Suspects for the radiation source behind
reionization had included supermassive black holes feeding on gas from
accretion disks surrounding them causing these regions to eject high-energy
radiation, large galaxies with masses in excess of 1 billion suns, and smaller
galaxies with masses less.
-
- Astronomers didn't think small galaxies
would be so efficient at producing ionizing radiation. It's four times higher
than what we expected, even for normal-sized galaxies.
-
- The JWST has spectroscopic capabilities in
the infrared. One of the reasons was to understand what happened during the
epoch of reionization.
-
- General relativity suggests all objects of
mass warp the very fabric of space and time, which are, in truth, united as a
single entity called "spacetime." Our perception of gravity arises as
a result of that curvature. The greater the mass of an object, the more
"extreme" the curvature of spacetime is. Thus, the stronger its
gravitational effects are.
-
- Not only does this curvature tell planets
how to move in orbits around stars and, in turn, tell those stellar bodies how
to orbit the supermassive black holes at the centers of their home galaxies,
but it also changes paths of light coming from the stars.
-
- Light from a background source can take
different paths around a foreground object as it travels toward Earth, and the
closer that path is to an object of great mass, the more it gets
"bent." Thus, light from the same object can arrive to Earth at
different times as a result of the foreground, or "lensing," object.
-
- This lensing can shift the location of the
background object in the sky, or it can cause the background object to appear
in multiple places in the same image of the sky. Other times, light from the
background object is amplified, and thus that object is magnified in the sky.
-
- This effect is "gravitational lensing," and the
JWST has been using it to great effect to observe ancient galaxies near the
dawn of time, which it would otherwise have had no chance of seeing. To observe the newly studied distant and
early dwarf galaxies, and analyze the light they emit, the JWST used a galaxy
cluster “Abell 2744” as a gravitational lens.
-
- Cosmologists are wrestling with how much
clumpiness does the Universe have?
The eROSITA X-ray instrument
orbiting beyond Earth performed an extensive sky survey of galaxy clusters to
measure matter distribution (clumpiness) in the Universe.
The cosmological parameters
that we measure from galaxy clusters are consistent with state-of-the-art
cosmic microwave background, showing that the same cosmological model holds
from soon after the Big Bang to today.
-
- The idea is to figure out just what the
Universe has been like through time. That means understanding matter, its
distribution (or clumpiness), and what role dark matter and dark energy have
played. It all began just after the Big Bang when the Universe was in a hot,
dense state. The only things existing were photons and particles.
-
- The Universe expanded and began to condense
into regions of higher density. As
things cooled and expanded, the denser clumps in the soup became galaxies and
eventually galaxy clusters. The clumpiness was smoother (or “isotropic”) than
expected. That raises questions about the role of dark matter and dark energy.
-
- Both dark matter and visible matter
(baryonic matter), make up about 29 percent of the total energy density of the
Universe. Presumably, the rest consists of dark energy, which we don’t know
much about, yet. Energy density is the amount of energy stored in a region of
space as a function of volume. In cosmology, it also includes any mass in that
volume of space.
-
- The measurement of energy density agrees
with measurements of the cosmic microwave background radiation, CMB. Think of
that as a map of the density variations in the early Universe. It’s made up of
microwave radiation that permeates the Universe. That radiation is not
completely smooth or uniform. That’s the variability in density that eventually
became the seeds of the first galaxies.
-
- eROSITA’s goal is to measure the assembly
of galaxy clusters over cosmic time. By tracing their evolution via the X-rays
emitted by hot gas, the instrument traced both the total amount of matter in
the Universe and its clumpiness. Those measurements solve the “tension” or
discrepancy between past clumpiness measurements that used different
techniques. Those included the CMB and observations of weak gravitational
lensing.
-
- The eROSITA data shows the distribution of
matter is actually in good agreement with previous measurements of the CMB.
That’s good news because cosmologists were afraid they’d have to invoke “new
physics” to explain the tension between measurements. eROSITA tells us that the Universe behaved as
expected throughout cosmic history.
-
- The eROSITA measurements of galaxy clusters
and other large structures also provide information about neutrinos. They’re
the most abundant particles with mass that we know of in the Universe. They
come from the Sun and supernovae, but also originated in the Big Bang. eROSITA’s survey offers new information about
the mass of neutrinos and their prevalence.
-
- Neutrinos may be small and tough to “see”,
but they have mass that contributes to the total density of matter in the
Universe. Cosmologists describe them as “hot”, which means they travel at
nearly the speed of light. Therefore, they tend to smooth out the distribution
of matter which can be probed by analyzing the evolution of galaxy clusters in
the Universe.
-
- This new look at clumpiness in the
Universe comes from the first release of data from eROSITA. The instrument
completed additional surveys in early 2022. Once those data are analyzed,
astronomers expect to be probing even deeper into the distribution of matter in
the Universe and testing their models against reality.
-
-
March 5, 2024 UNIVERSE -
clumpiness of galaxies? 4377
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------ “Jim Detrick” -----------
--------------------- --- Wednesday, March 6,
2024
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