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------------ 1889 - Evolution of the galaxies
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- 150 million years after the Big Bang the first stars were so large and bright in ultraviolet light that the UV radiation ionized the neutral hydrogen gas. The UV radiation separated the electrons from the nuclei in the hydrogen atoms. The re-ionization broke the UV light free to travel throughout the Cosmos. Before this happened the Universe was opaque, like looking at the surface of a white cloud. After this happened the Universe became transparent and light filled the heavens.
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- Today, galaxies found at Redshifts of 7 or greater contain 1st generation stars and some galaxies have a large bubble of ionized gas around them. Galaxies difficult to see are having their light blocked by neutral hydrogen gas. Dimmer galaxies did not have the hot stars and UV light needed to break up the neutral hydrogen gas. The fainter galaxies became shrouded from view. Neutral hydrogen represented a “ Cosmic Fog
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- To find these earliest galaxies astronomers must look in the infrared wavelengths because the light has been “ redshifted” traveling long distances in expanding space. As space stretches these wavelengths towards the red end of the spectrum. Also, to collect the dim light telescopes must stare at the same spot in the sky for long durations to detect these earliest and faintest galaxies. Sometimes exposures have lasted over 1,000 hours.
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- The images of these distant, earliest galaxies are as they were billions of years before the Earth and the Solar System were even formed. By tracking this evolutions through time astronomers hope to learn how the early Universe formed and in particular how Dark Matter played a role in our evolution.
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- Japan’s Subaru telescope in Hawaii has measured clusters of galaxies some 13 billion lightyears from Earth. Measuring 3,000 ancient galaxies velocities and positions consistently confirm the equations in Einstein’s General Theory of Relativity. They further show that Dark Energy and Dark Matter are playing their roles in the expansion of the Universe.
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- Computer modeling, or “ simulation”, experiments with different scenarios until a good match exists to observations. To recreate the Milky Way and the 26 galaxies in out Local Group of galaxies that are locked in their mutual gravitational forces we need “ halos” of Dark Matter.
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- Not just one massive halo but many thousands of smaller sub-halos. The smaller galaxies formed are called “ satellite galaxies”. These galaxies can orbit their host galaxy for billions of years. Many merge causing the central galaxy to add large amounts of gas and stars. These mergers trigger violent episodes of new star formation.
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- Smaller halos form “ dwarf galaxies” which may be orbited by even smaller satellite sub-halos of Dark Matter. This scenario readily appears in theoretical models run in computer simulations. This mechanism offers an explanation to the origin of isolated spheroid dwarf galaxies orbiting the larger Milky Way and Andromeda galaxies.
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- Now, lets look at “ observations” of our own Milky Way Galaxy:
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- The Milky Way is made up of two main populations of stars. The young metal- rich stars are in the disk. And , the older, metal-poor stars are in the galaxy’s halo of stars.
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- The Sun has orbited in nearly a perfect circle of the galactic center on which it was born. It is on its 18th trip. The young thin disk in which it resides is only 300 lightyears thick broadening to 1,000 lightyears at the Sun’s radius of 26,000 lightyears. The galaxies thick disk of older stars is 3,000 lightyears thick.
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- The galactic center is a Blackhole some 4,000,000 Solar Mass. The galactic halo enveloping this center comprises the oldest metal-poor stars. If you extend the outer halo you reach some 100 small satellite galaxies.
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- Beyond this halo of small galaxies is a the halo of Dark Matter holding all this dynamic mass together. The Dark Matter halo spans 600,000 lightyears containing a trillion Solar mass of material.
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- Theory has it that this formation for our galaxy started some 10 billion years ago and evolved into a flattened disk some 8 billion years ago.
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- Our Milky Way Galaxy is still accreting smaller dwarf galaxies. And, there are stars in the galaxy’s central bulge that are older than the galaxy itself. Some stars were formed some 300 million years after the Big Bang. Of the 14,000 stars studied 500 are older-metal-poor stars. 23 of these are so metal-poor that they are nearly pure hydrogen and helium. They must be at least 13.5 billion years old.
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- Our galaxy’s biggest merger is still in our future. The Milky Way will merge with the Andromeda Galaxy some 4 billion years from now. Meanwhile our Milky Way galaxy is swallowing dwarf galaxies. One example is the Sagittarius dwarf spheroid galaxy that is currently falling into our Galaxy’s halo.
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- If we look at the Milky Way using different frequencies beyond visible light we see the infrared heat coming from dust in the galaxy. We call it heat but it is -251 Celsius. Empty space is -273 Celsius.
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- Add higher frequency exposes carbon monoxide gas where new stars are being born. Higher frequencies still expose charged particles caught in magnetic fields. These particles can be accelerated to nearly the sped of light causing them to radiate very high frequency energy. Still another frequency is tuned to the radiation created when free particles zip past each other without colliding. This occurs in hot, ionized gas near massive stars.
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- These images come from the Planck Space Observatory launched by the European Space Agency in 2009. Studies continue to learn about our home in the Universe and how we got here. The biggest miracle in the Universe still is that we are here thinking about how we got here. Stay tuned, an announcement will be made shortly.
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- Request these Reviews to learn more about the Milky Way Galaxy:
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- #1804 - Placing 1,000 Milky Ways end for end spans 100 million lightyears which is the size of the Virgo Cluster of galaxies.
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- #1703 - Many of the dwarf galaxies that were swallowed up by the Milky Way have left streams of stars stretching across the sky.
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- #1526 - The galaxy center is like a pin ball machine.
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- #1492 - The diameter of the bulge at the center of the galaxy is 8,000 lightyears.
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- #1348 - During the time it took light from 13.7 billion lightyears to reach us the Universe has grown to 45 billion lightyears.
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- #1337 - The gas falling into the Blackhole at the center emits 50 times more energy than hydrogen-helium fusion would.
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- #1337 - this review lists 8 more earlier reviews about the Milky Way Galaxy
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
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- to: ------- jamesdetrick@comcast.net ------ “Jim Detrick” -----------
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----- 707-536-3272 ---------------- Wednesday, July 6, 2016 -----
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