- 4057 - EARLIEST GALAXIES - was this the beginning? The James Webb Telescope (JWST or Webb) has unveiled hundreds of ancient galaxies that could be among the first members of the universe. As early as 600 million years after the Big Bang, these very young galaxies had complex structures and clusters of star formation.
--------------- 4057 - EARLIEST GALAXIES - was this the beginning?
- JWST has gathered
observations from two tiny patches in the sky.
One in the Ursa Minor
constellation and another in the direction of the Fornax cluster. Within this
region were over 700 newly discovered young galaxies that reveal with the
universe looked like in its earliest beginning.
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- If you took the whole
universe and shrunk it down to a two hour movie, you are seeing the first five
minutes of the movie. These are the
galaxies that are starting the process of making the elements and the
complexity that we see in the world around us today.
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- In those five minutes
alone, which marks the universe to be between 370 million and 650 million years
old, they found 717 young galaxies with
all of them already spanning thousands of light-years, sporting complex
structures, and birthing stars in multiple clusters.
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- Previously, the
earliest galaxies we could see just looked like little smudges. And yet those
smudges represent millions or even billions of stars at the beginning of the
universe.
-
- Despite previous
scrutiny, 93% of the newfound galaxies that Webb spotted had never been seen before. Precisely how that chaotic, very dusty
environment cleared up to become the transparent cosmos we see today has long
been debated.-
-
- A leading theory is
that this phase of evolution of the universe, called the Epoch of Reionization,
occurred some 400,000 years after the Big Bang, when the first generation of
stars, thought to be 30 to 300 times our sun's mass and millions of times more
bright, formed and flooded the opaque universe with its first light.
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- That ultraviolet
starlight reionized the universe by splitting its abundant hydrogen atoms into
protons and electrons, a process that lasted until one billion years after the
Big Bang. However, outflows from supermassive black holes, similar to the one
that resides in the heart of our Milky Way, could have triggered the escape of
ultraviolet radiation from galaxies and thus played a more important role in
cosmic evolution than previously thought.
-
- Astronomers are
studying galaxies that existed between 500 to 850 million years after the Big
Bang, or between five to eight minutes of the two-hour movie describing the
universe, thinks they have an answer to the long-standing question.
-
- Galaxies in the very
early universe were just far more chaotic in general in how they formed
stars. One in six galaxies at the time
showed extreme line emissions in the galaxy's spectra, a feature that atoms
ionized by starlight radiate when they have cooled down and combined with other
molecules.
-
- Those emission lines are
evidence that early galaxies were actively birthing stars, which then pumped
"torrents of ultraviolet photons" into their respective galaxies.
This way, the universe's early stars became the main drivers of cosmic
reionization.
-
- These extreme emission
lines are actually relatively common in the very early universe. Almost every single galaxy that we are
finding shows these unusually strong emission line signatures indicating
intense recent star formation. These
early galaxies were very good at creating hot, massive stars.
-
- All of a sudden you
would have tens of suns worth of solar masses being assembled all at once in
these early galaxies. That's really
important for our understanding of how reionization happened because these hot
massive stars were very efficient producers of these ultraviolet photons that
we needed in order to ionize all the hydrogen in the early universe.
-
- Shortly after the Big
Bang, the universe was a dark and mysterious place. The gas between stars and galaxies was
opaque, so no light could shine through. As anyone who's ever looked through a
telescope knows, that's no longer the case, since we can see celestial objects
all throughout the universe from our vantage point here on Earth. But what caused
the change in opacity?
-
- This was back in time
at galaxies from the end of the “Era of Reionization”, a dramatic period in the
universe's history in which gas was heated, cooled and then reionized, given an electrical charge once again.
-
- More than 13 billion
years ago, during the Era of Reionization, the universe was a very different
place. The gas between galaxies was largely opaque to energetic light, making
it difficult to observe young galaxies. What allowed the universe to become completely
ionized, leading to the "clear" conditions detected in much of the
universe today?
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- Looking at those early
galaxies, which existed just 900 million years after the Big Bang, astronomers
saw that most of the gas in the universe was somewhere between opaque and
transparent. But directly around the galaxies, everything was clear.
-
- We are seeing galaxies
reionize the gas around them. Imagine
that each of these young galaxies was surrounded by a balloon. Energy from
newly forming stars reionized the gas inside that balloon. As the galaxies
grew, the bubbles of reionized gas merged, creating even larger pockets of
transparency. Eventually, they all combined to create a transparent universe.
-
- This phenomenon could
be seen in action thanks to the illumination of a quasar, an extremely bright
supermassive black hole. Turning Webb toward one particular quasar, the
astronomers observed its light moving through the universe's gas, being
absorbed by opaque gas in some areas and traveling through transparent gas in
others.
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- By illuminating gas
along our line of sight, the quasar gives us extensive information about the
composition and state of the gas. Next,
the team will more deeply research galaxies in five other areas of the sky that
all have a central quasar, shedding more light on the opacity of the early
universe.
-
-
June 16, 2023 EARLIEST GALAXIES
- was this the beginning? 4057
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