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Stellar mass black holes vs. supermassive black holes
* Stellar mass black holes form from the collapse of massive stars at the ends of their lives, so they have roughly the same mass as a star. Supermassive black holes are physically identical to their smaller counterparts, except they are 10 thousand to a billion times the size of the sun. However, their formation is more of a mystery. They may form from the merging of smaller black holes.
Supermassive black holes at the center of galaxies
* Almost every large galaxy has a supermassive black hole at its center, but researchers are not yet sure (https://jila.colorado.edu/research/astrophysics/black-holes-galaxies) why that’s the case, how they originate, and what their role is in the creation and evolution of galaxies.
Why are stars different colors?
* The color of a star depends on its temperature (http://www.atnf.csiro.au/outreach/education/senior/astrophysics/photometry_colour.html). The hotter a star, the higher energy its light will be. Higher energy/temperature corresponds with the blue end of the visible spectrum and lower energy/temperature corresponds with the red end.
How does dark matter make stars spin faster?
* In the 1960s, astronomers Vera Rubin and Kent Ford noticed that stars at the edges of galaxies were moving just as fast as stars at the center, which surprised them: it appeared that the force of gravity causing stars to orbit the center of the galaxy was not weakening over distance. Their observation implied that something else, distributed throughout the galaxy, was exerting a gravitation pull. We now know that that “something else,” now named dark matter, accounts for about 85% of the matter in the universe. (It existence was inferred in the 1930s, when the astronomer Fritz Zwicky(http://www2.astro.psu.edu/users/rbc/a1/week_10.html) noticed that galaxies in clusters were moving faster than they should.)
Size of the universe
* The universe is only 13.8 billion years old, but has a radius of about 46 billion light-years. If nothing can travel faster than the speed of light, how can that be? The expansion of the universe, driven by dark energy, is causing distances between objects to grow. Note that it is not moving those objects apart; rather, it is increasing the amount of space between them. https://phys.org/news/2015-10-big-universe.html
* Galaxies are not distributed randomly (http://skyserver.sdss.org/dr1/en/astro/structures/structures.asp) in space; instead, clusters of galaxies form web-like patterns. These webs consist of filaments, where dark matter and ordinary (baryonic) matter are concentrated, and voids, where galaxies are scarce. Researchers believe that these large-scale structures grew out of minor fluctuations in density at the beginning of the universe.
Composition of the early universe
* Moments after the Big Bang, the universe formed the nuclei for what would be come the universe’s hydrogen and helium atoms, with one helium nucleus for every 10 or 11 hydrogen (http://umich.edu/~gs265/bigbang.htm). When the first stars formed, there were no heavier elements — those elements formed inside stars.
String Theory Landscape
* The String Theory Landscape is a theory that the universe we live in is one of many universes. It attempts to explain how certain constants of nature seem “fine-tuned” for life, which contradicts the anthropic principle, or the notion that we humans hold a special place in the universe. https://www.scientificamerican.com/article/multiverse-the-case-for-parallel-universe/%0A
Disintegration of the universe
* In the future Degenerate Era of the universe, as space-time expands and stars burn up, all of the matter in stars will be consumed by black holes. But even black holes are not forever. Stephen Hawking theorized that black holes will slowly radiate away their mass in what is now called Hawking radiation until they too dissipate away. http://www.nytimes.com/books/first/a/adams-universe.html
Music provided by APM
Sound effects: Freesound.org
– Galaxy within Universe: Edgeworx;
– Stars at center of Milky Way – NASA/NCSA University of Illinois Visualization by Frank Summers, Space Telescope Science Institute, Simulation by Martin White and Lars Hernquist, Harvard University
From the producers of PBS NOVA
© WGBH Educational Foundation
Funding provided by FQXi
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ESA Euronews: The dark side
Space science: everything starts here
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