17

This is the Newtonian model of gravity. It is a very good model, it is used for accurate calculating the motion of objects in the solar system to a very high degree of accuracy. However, for very strong gravitational fields you need to use Einstein's model, which accounts for things like the constant speed of light for all observers. I'm not going to go into ...


13

It is not well known, but a paper by M. Brightman et al gives a value of $10^{6.3\pm0.4}$ or between 8 hundred thousand and 5 million solar masses, while noting that this estimate is lower than previous estimates which had $10^{6.95}$ or about 9 million masses. It seems that, although the galaxy is face-on to us, its black hole is viewed from the edge. This ...


5

No, the light doesn't just disappear, it adds to the black hole's mass in accordance with $E=mc^2$. So if a star produced light from $m$ kilograms of mass and all that light fell into a black hole, the black hole's mass would increase by $m$ kilograms.


4

Not really my area, but this question is probably related to the planetary migration in circumstellar disks. In this case, the migration is caused by gravitational interactions between the planet and the gas in the disk. There are two explanations for this effect Impulse approximation: consider a parcel of gas in the corrotating frame. If the gas is close ...


2

The introduction of the Wyrzykowski & Mandel paper gives the following information about estimating the lens mass. In order to obtain the mass of the lens (Gould 2000a), it is necessary to measure both the angular Einstein radius of the lens ($\theta_\mathrm{E}$) and the microlensing parallax ($\pi_\mathrm{E}$) $$M = \frac{\theta_\mathrm{E}}{\kappa \pi_\...


2

A gravitating object in a disk creates a wake on the inner edge of its orbit as well on the outer edge of its orbit. The inner wake is the leading wake, while the outer wake is trailing. The torques created by these two wakes would cancel, if the disk had no shear. Yet disks in astrophysical contexts are subject to Keplerian shear - and thus the torques ...


1

Maybe, Harvard scientists have proposed a way to determine, once and for all, whether Planet Nine actually could be a black hole. Specifically, the new method would scour the outer solar system for evidence of telltale flares that are emitted when a black hole devours a comet or other distant object. Such flares, they say, should be detectable by the ...


1

At the moment that two black hole interiors merge into one, there's a bridge between the event horizons, as you can see in simulations like this one (20 second silent YouTube video). While it may look like the protrusions on the event horizons form shortly before the merge, they're actually present (though very small) all the way back to the formation of the ...


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