Sunday, May 7, 2023

3988 - BIG BANG - James Webb new look?

 

-   3988  -   BIG  BANG  -  James Webb new look?    The James Webb Space Telescope (JWST) appears to be finding multiple galaxies that grew too massive too soon after the Big Bang, if the standard model of cosmology is to be believed.


------------  3988  -   BIG  BANG  -  James Webb new look?

-   The six earliest and most massive galaxy candidates observed by JWST so far stand to contradict the prevailing thinking in cosmology. That's because other researchers estimate that each galaxy is seen from between 500 and 700 million years after the Big Bang, yet measures more than 10 billion times as massive as our sun.

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-   One of the galaxies even appears to be more massive than the Milky Way, despite that our own galaxy had billions of more years to form and grow.  If the masses are right, then we are in uncharted territory.

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-   We require to learn something very new about galaxy formation or a modification to cosmology. One of the most extreme possibilities is that the universe was expanding faster shortly after the Big Bang than we predict, which might require new forces and particles.  For galaxies to form so fast at such a size, they also would need to be converting nearly 100% of their available gas into stars.

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-   We typically see a maximum of 10% of gas converted into stars.  So while 100% conversion of gas into stars is technically right at the edge of what is theoretically possible, it's really the case that this would require something to be very different from what we expect.

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-   If the masses and time since the Big Bang are confirmed for these galaxies, fundamental changes to the reigning model of cosmology.

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-    The dark energy + cold dark matter (ΛCDM) model has guided cosmology since the late 1990s.  But this means the model needs to change. If there are other, faster ways to form galaxies than ΛCDM allows, or if more matter actually was available for forming stars and galaxies in the early universe than was previously understood, astronomers would need to shift their prevailing thinking.

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-    The six galaxies' times and masses are initial estimates and will need follow-up confirmation with spectroscopy. 

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-   A Spectroscope splits the light into a spectrum and analyzes the brightness of different colors.   Such analysis might suggest that central supermassive black holes, which could heat up the surrounding gas, may be making the galaxies brighter so that they look more massive than they really are.

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-  Or perhaps the galaxies are actually seen at a time much later than originally estimated due to dust that causes the color of the light from the galaxy to shift redder, giving the illusion of being more lightyears away and, thus, further back in time.

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-    Another ongoing collaborative JWST project, “COSMOS-Web” may be involved with spectroscopy and shedding more light on the findings to help resolve the dilemma. COSMOS-Web is covering an area roughly 50 times larger than CEERS and is expected to discover thousands of galaxies.

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-    It will be ideal for discovering the rarest, most massive galaxies at early times, which will tell us how the biggest galaxies and black holes in the early universe arose so quickly.

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-    The James Webb is also getting closer to finding what ionized the Universe.  Astronomers have determined that “leaky” galaxies may have been responsible for triggering the last great transformational epoch in our universe, one which ionized the neutral interstellar gas.

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-    Billions of years ago our universe was a lot smaller and a lot hotter than it is today. At very early times it was so small and hot that it was in the state of a plasma, where electrons were separated from atomic nuclei.

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-    When the universe was 380,000 years old, it cooled to the point that electrons could recombine onto their nuclei, forming a soup of neutral atoms.

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-   However, observations of the present-day universe reveal that almost all the matter in the universe is not neutral at all. Instead it’s ionized, once again in the state of a plasma. Something had to happen in the intervening billions of years to transform the neutral gas of the cosmos into an ionized plasma.

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-     Astronomers call this event the “Epoch of Reionization” and suspect that it happened within the first few hundred million years after the Big Bang. But they are not sure how this transformational event proceeded.

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-   One of the great debates in modern cosmology is the source of this reionization. One hypothesis is that quasars are responsible. Quasars are the ultra bright cores surrounding supermassive black holes which pump out enormous amounts of high energy radiation. This radiation could easily flood the universe and transform it from neutral to ionized.

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-    But the problem with this hypothesis is that quasars are relatively rare, and so they have difficulty covering the volume of the universe.

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-   Another hypothesis is that young galaxies rich with star formation are responsible. In this scenario the process of ionizing the neutral gas is more spread out throughout the universe.

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-    Each individual galaxy is only capable of ionizing the gas in its nearby vicinity, but since there are so many galaxies it’s possible to reionization the entire universe. But the only way to do this is if enough high energy radiation leaks out of galaxies and into the surrounding medium.

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-    The James Webb Space Telescope is being ussd to investigate this hypothesis. They can’t study the radiation coming out of the galaxies directly, because that radiation gets absorbed by the billions of light-years worth of matter between us and those galaxies.

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-   Instead they had to look for other clues. Using the James Webb’s ability to study distant galaxies, they were able to measure how compact the galaxies were, and how rich in star formation they were. They were then able to compare these galaxies to similar galaxies found in the present day universe to create an estimate of the amount of radiation leaking from them.

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-    They estimate that on average the galaxies in the early universe leaked roughly 12% of their available high energy photons. This is just enough to potentially reionization the entire cosmos in a relatively short amount of time.

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-    The results are not conclusive because of the number of assumptions that the astronomers had to make. But it does point in an intriguing direction in solving this long-standing cosmic riddle.

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                 May 6, 2023         BIG  BANG  -  James Webb new look?          3988                                                                                                                          

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--------------------- ---  Sunday, May 7, 2023  ---------------------------

 

 

 

 

         

 

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