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There certainly are quasars. Obviously, we can't see any as they are today because they aren't nearby. Quasars are a type of Active Galactic Nucleus(AGN), which means we won't find any within our local few million lightyears. However, as the Wikipedia page on Quasars will tell you, any time a supermassive black hole of a galactic nucleus gets a massive ...


The best evidence for the black hole at the center of the Milky Way comes from the simple Keplerian motion of nearby stars. Using orbital data deduced by scientists, I made a simulation of their motion. Please note that this simulation needs a browser that supports WebGL.


You are correct about the bias factor - because the dark matter distribution is not measured directly, but via tracers (galaxies), there may be some bias in the tracers. This is put into the analysis as an unknown bias parameter $b$ that needs to be fit. Now the second part of your question - why do we care about the dark matter? Briefly, it is because the ...

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