Sunday, April 30, 2023

3978 - X-RAY GALAXIES - new revelations.

 

-   3978 -   X-RAY  GALAXIES  -  new revelations.    Astronomer's will depend on getting more data from “simulated galactic clusters”. SLAC cosmologists are currently attempting to expand the size of computer simulations of the cosmos while improving accuracy.


---------------------  3978  -   X-RAY  GALAXIES  -  new revelations.

-    A new investigation of the structure of galaxy clusters has found it agrees with predictions made by the standard model of cosmology, the best explanation scientists have of the evolution of the universe over its 13.8 billion-year existence.

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-    The SLAC National Accelerator Laboratory at Stanford University, measured X-ray emissions from clusters of galaxies to reveal the structure of these clusters and the distribution of matter throughout them.

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-    The data they collected conform to a model of universal evolution and structure called the “lambda cold dark matter” (ΛCDM) model, which suggests that the infant universe was an extremely hot, dense sea of photons and matter tightly coupled as plasma.

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-    As the infant universe underwent a period of rapid expansion called “inflation:, small perturbations spread through the plasma as a sound wave, producing under- and over-densities of both matter and radiation, but not affecting dark matter.

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-    According to the ΛCDM model, the plasma expanded and cooled, and electrons and protons soon combined to form the first atoms, with free electrons no longer infinitely scattering photons.

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-     This allowed the universe to become transparent to light. Overdense regions collapsed to birth the first stars, and the universe eventually reached its current state, with clusters of galaxies as the largest bound objects linked by a vast cosmic web of dark matter.

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-    Confirming this ΛCDM model by inferring the mass distributions of galactic clusters from X-ray emissions was no easy task.   It is easier to use X-ray emissions as a measurement of mass distribution when the energy of the gas in clusters is balanced by the pull of gravity as it binds the entire system.

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-    This balance is achieved when galaxy clusters have settled down into a "relaxed" state.  When researchers compare real observations with the theoretical predictions of the ΛCDM model, they must take into account that there has been a bias toward selecting these "relaxed" galaxies.

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-     Redshift is the stretching of the wavelength of light that occurs as a result of the expansion of the universe. The farther light has traveled, the more it is shifted toward the red end of the electromagnetic spectrum. That means the earlier and more distant the galaxy, the more extreme the redshift, thus making this a great measure of both distance and age.

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-    This research has found that over the universe's 13.8 billion-year existence, clusters have become more centrally concentrated. At the same time, at any given epoch of the universe, less massive clusters are more centrally concentrated than more massive ones.

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-     When the Vera C. Rubin Observatory opens its eye on the universe, it will begin the “Legacy Survey of Space and Time”, which should spot far more galaxy clusters. Joining this quest will be the fourth-generation cosmic microwave background experiment, while the European Space Agency's Athena satellite mission will follow up with more X-ray measurements.

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                   April 29, 2023     X-RAY  GALAXIES  -  new revelations.             3978                                                                                                                          

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--------------------- ---  Sunday, April 30, 2023  ---------------------------

 

 

 

 

         

 

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