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No, black holes are not the only cause of HVSs, although it is thought to be the most common mechanism. Hyper velocity stars are believed to be caused when binary stars come close enough to a supermassive black hole for one of the pair to be captured while the other star is ejected at high velocity. This appears to the main mechanism for HVSs. See for ...


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Ultimately we don't know enough about exoplanets to be sure; for now all our data is skewed toward more massive planets which are easier to detect using Doppler wobble, or large diameter planets (almost certainly gas giants) which are easy to detect by their host star dimming when they eclipse it relative to us. More data is coming in every day, and as ...


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The Earth doesn't cover the hole, the Earth is the hole. Gravity is an attractive force, so were you not standing on the Earth, the Earth's gravity would cause you to accelerate towards it. As you are standing on the Earth, you feel this acceleration as your weight, just as you would feel pressure if you were to push against a wall. To take a more complex ...


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In terms of dark matter, there are two notions which are incorrect. One is that dark matter is a clump of stuff traveling with the matter. The other is that dark matter does not interact with matter. Dark matter fills 'empty' space. Dark matter is displaced by matter. The Milky Way moves through and displaces the dark matter. The Milky Way's halo is the ...


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Also asked at http://physics.stackexchange.com/questions/174080/how-do-we-know-dark-matter-isnt-curved-spacetime Basically no. Or at least you can't have this idea and General Relativity. GR demands that you have something (matter/energy density) to cause the curvature. Curvature without cause is not part of the model. That's not to say that what you ...


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Let's assume that what is falling onto the neutron star is "normal" material - i.e. a planet, an asteroid or something like that. As the material heads towards the neutron star it gains an enormous amount of kinetic energy. If we assume it starts from infinity, then the energy gained (and turned into kinetic energy) is approximately (ignoring GR) $$ ...


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We have observed impacts with Jupiter In 1993 comet Shoemaker Levy 9 impacted. In 2009 an unknown object impacted. In each case the object was destroyed in Jupiter's atmosphere.


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I think there are two key aspects to the answer. 1) Solid/rocky bodies should tend to collide before they reach the Roche limit. 2) When gaseous bodies reach the Roche limit (and undergo 'Roche-Lobe Overflow'), the dynamics are basically those of test-bodies and are fairly straightforward and well understood from binary stellar dynamics. To expand on ...


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You can see an example of tidal locking and atmosphere simulation for a planet closely orbiting a dim star. They show a simulation of the atmosphere and some interesting theories about the movement of gasses due to tidal locking (convection) that occurs between the bright and dark side of the planet. The link goes directly to the discussion of tidal ...


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Yes, the formula you quote applies to some extend. It can also be written in terms of Boltzmann's constant $k_\mathrm{B}$ as $$v_\mathrm{rms} = \sqrt{\frac{3k_\mathrm{B}T}{m_\mathrm{m}}},$$ with $m_\mathrm{m}$ the mass of the molecule in question, gives the mean ("root-mean-square") velocity of the gas molecules as a function of temperature $T$. Comparing ...



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