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Well there is two answers: 1. It is not infinite. At a point when the black hole has taken in lots of matter, it will throw some out of the black hole to again be able to take in matter.It is like the biggest foodie in the world who can eat a lot but at a point when his tummy is full, he needs to throw up or wait until he can take in more. 2. It is infinite. ...


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Black holes are in the realm of General Relativity. In GR even the law of conservation of energy is under question when approaching singularities of the GR solution. Potential energy is a concept that comes with conservation of energy. Where the singularity in the black hole solutions is dominating, one cannot talk in terms of energy conservation and ...


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Your question What is the potential energy of a black hole? doesn't make sense because energy is a somewhat tricky concept to deal with in GR. If we treat the black hole as fixed we can study the motion of a test particle falling into it, and we find that there is a quantity analogous to total energy that is constant as the particle falls in. So in ...


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You could try measuring the effects of the Lense-Thirring effect. It is an example of frame dragging. Essentially, an object that is orbiting near a massive object that is also rotating will have its axis undergo a change in its orientation. There are two problems here: The rotating object must be large. The rotating object must not be rotating slowly. ...


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One can use the Doppler effect, which will shift spectral lines to the red at the side the rotates away from us and towards the blue on the side that rotates towards us. This is being used by astronomers who measure "rotational broadening" on stars which can not be resolved in telescopes. In that case it's all about measuring the rate of rotation, of course, ...


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You have$\frac E{m_0}$, the energy divided by the rest mass is $\gamma=\sqrt{1-\frac{v^2}{c^2}}$. The proper time is lab time divided by $\gamma$. Since you have a fixed $E$, as $m_0 \to 0, \gamma \to \infty$ and the proper time goes to $0$. For the last part, you are supposed to assume that an $11$ MeV neutrino arrived $7$ seconds before a $7$ MeV ...


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Stars orbiting black holes (I assume that's what you mean) and observed from afar will have their light doppler shifted due to (i) gravitational redshift; (ii) the relativistic doppler effect due to their orbital motion. Effect (i) becomes more important the closer a star gets to the event horizon of the black hole. The redshifted frequency is given by ...


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Yes, they absolutely would. In general, a light-ray which passes at a minimum distance $x$ to the BH will have all of the same effects as a light-ray emitted at the same distance $x$.


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The invisible mass in the universe as you mentioned refers to mass which is not visible using electromagnetic radiation. It is called dark matter and was detected by the virtue of its gravitational effects. The diameter of the universe doesn't play much role in your question. Secondly, there can be many massive things which can't be seen by EM radiation but ...


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There are very high energetic cosmic rays. The most energetic cosmic rays measured by the Auger observatorium for example have energies in excess of $10^{19}$ eV. They measure a few of those per year. At these energies they are no longer able to identify what type of particle it is, but it is believed to be predominantly protons and iron. These particles are ...


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This is a somewhat odd question since average is a somewhat vague term. Are you referring to temperature averaged by total mass? Or average temperature by volume? As mentioned in the comment above, the most important "Universal temperature" is the temperature of the Cosmic Microwave Background which is basically the light that was released when the ...


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Without knowing much about Jean's instability I can probably help you with the derivation of the expression. You start with the expression in 1) and expand it to first order in $\delta P$ and $\delta R$. Then you use that $R_0$ and $P_0$ are stationary solutions i.e $\ddot{R_0}=0$ thus $GmM/R_0^2= 4 \pi R_0^2 P_0$. You can use this to simplify the ...


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According to wikipedia the orbital period of Planet 9 is 10,000–20,000 years. This means it would take a minimum of 5,000 years to switch between perihelion and aphelion. So - even our best historical observation data of kuiper belt objects is just a tiny fraction of the time it takes for Planet 9 to move in it's orbit. There's not really sufficient ...


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Your case is not quite watertight - it hinges in your assertion that the optical light that is seen comes from some way out from the black hole (SMBH). The thing is that gravitational redshift can be larger than 0.2 and it is also aided by the relativistic transverse Doppler effect in the orbiting material. Some details: Gravitational redshift around a ...


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From Wikipedia, from New Scientist According to Krzysztof Stanek of Ohio State University, one of the principal investigators at ASAS-SN, "If it was in our own galaxy, it would shine brighter than the full moon; there would be no night, and it would be easily seen during the day."[6] [6] ...


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Coadding is not an especially precise term, I don't think, but in general it just means stacking or combining images --- very literally, just 'adding-together'. I usually hear this in terms of stacking images of the same field (e.g. of an optical image), but I think it can also be used to mean mosaic images, even in arbitrary parameter spaces. See for ...


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Metallicity is irrelevant if the stellar gas cloud has enough mass when it begins to collapse. The Chandrasekhar limit gives the following limit; $$M_{limit} = \dfrac{\omega_{3}^{0}\sqrt{3\pi}}{2}\left(\dfrac{\hslash c}{G}\right)^{\frac{3}{2}}\dfrac{1}{\left(\mu_e m_H\right)^2} = 1.39 M_\odot$$ that can be applied to any composition of Fermi gases. The ...


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The negative sign for the partial decay widths denote the sign of the corresponding reduced width amplitude in the R-Matrix formalism, which is what the author of this paper (and everybody else analyzing cross sections of low-energy nuclear reactions) is using to do his analyses. He's using the R-Matrix code SAMMY, which sadly has very little documentation. ...


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I'd say no, though the paper seems credible in its methods I believe it is neglecting to account for the fact that we can only measure the Visible Universe. This may require a little explanation as I don't mean there are some extra layers or dimensions, but that we can only see $\dfrac{4}{3}\pi(14.5\cdot 10^{9}\ \mathit{ ly})^{3}$ of the Universe due to the ...


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I make two suggestions. 1. "Planetary and Interstellar Processes Relevant to the Origins of Life." Edited by D. C. B Whittet. This was written in 1997, so it is a little dated, but it contains about 14 chapters, written by acknowledged experts, and it contains many references. It won't do everything you want, but it is a start, and as others mentioned, ...



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