Topic: Black Holes and TOV Limit

[arakish]

Started this thread since it was going off topic in original thread.

But isn't 3-20 solar masses (TOV limit on stellar black holes) a small enough figure and a large enough range that by varying mass and speed we might arrive at a better estimate of what happened, if we want to keep close to the original idea?

Possibly.  A 3 M_S black hole would have an event horizon of 9km.  It is theorized that black holes can actually grow as they eat more matter.  I tend to believe this, else how can one get those super monsters at galactic centers?  This kind of supercedes the hypothesis of black holes having infinite mass.

If the event horizon can grow as a black hole eats more matter (mass), does this not preclude that the singularity in its heart is infinite mass?

However, I hypothesize that a black hole's singularity is of infinite mass.  As one approaches the speed of light, mass increases.  If one were to go at the speed of light, mass becomes infinite (or undefined).  I don't have the equation on hand here at UNM, but I do remember, mass increases until the speed of light, then it becomes infinite.

Thus, by simple logic, if light cannot escape from a black hole's singularity, then the singularity must have infinite mass.  I know, really bad science, and probably even worse logic, but that is how I derive the fact that once a black hole forms, it is of infinite mass.

Besides, even if a black hole were to hit another celestial object, especially by direct impact, would it not simply "eat" that object and keep on going?

rmfr

[jdale]

Besides, even if a black hole were to hit another celestial object, especially by direct impact, would it not simply "eat" that object and keep on going?

I would think that depends on its speed. If it's going slow enough, yes of course. Certainly the parts of the object within the black hole's event horizon. But if it's going fast enough, matter may not have enough time to reach the black hole before it's gone. It's going to impart some momentum to them, but the matter still has to travel at finite speeds.

[Wolfhound]

Besides, even if a black hole were to hit another celestial object, especially by direct impact, would it not simply "eat" that object and keep on going?

I would think that depends on its speed. If it's going slow enough, yes of course. Certainly the parts of the object within the black hole's event horizon. But if it's going fast enough, matter may not have enough time to reach the black hole before it's gone. It's going to impart some momentum to them, but the matter still has to travel at finite speeds.

And this is part of the reason that it would rip apart the planetary body, not just punch through it, as it would pull apart a large portion of the core (in addition to the other effects already explained by arakish previously.

[Defendi]

I believe that a black hole has a mass and the singularity is infinite mass because at that point, physics is inherently broken.

Also  is captured by the event horizon because that is the point where the escape velocity is greater than the speed of light.  I don't know if that required infinite mass.

[jdale]

To punch through rather than shatter the whole, you just need enough momentum to overcome the shear strength of what you are punching through. In this case we also need enough momentum to not be significantly slowed by what we are running into, so that we can still overcome the shear strength as we are exiting. A black hole has a lot of mass to contribute to momentum, if we also have relativistic speeds it doesn't seem impossible to punch through.

Depends on the size though. Arakish's example with the 9 km event horizon is pretty small compared to the diameter of a planet. If there is a bunch of mass around the black hole (matter that hasn't fallen in yet), it will make a mess of the surface and maybe even get stopped by the planet while the denser black hole punches through.

[jdale]

I looked at the argument you posted elsewhere, and I think one issue is the assumption that all the energy transfers to the planet. You can calculate E = (mv^2)/2 and normally it's a fair assumption to say E must be applied to the planet, in the form of heat, etc, which will pretty much make a mess of things. There are only so many ways for that energy to be dissipated, and all of them are damaging.

However, if a significant amount of mass exits the planet on the other side, then the imparted E is going to be reduced by (mv^2)/2 of the exit mass.

[mistrornge]

So you're saying about a -100 penalty then?

[markc]

   +1 laugh
MDC

[Defendi]

We're talking about an object measured in stellar masses, are we not?  I can't imagine the sheer strength of a planet would matter at all, especially since it's accelerating the mass toward itself as it devours it (tearing it away).  A more significant effect would be that it's absorbing the mass into itself and so it's going to slow toward that mass's inertial frame and that mass is going to accelerate toward it.  Since the escape velocity is greater than the speed of light, it can't lose that new mass (except through Hawking Radiation).  Also the amount slowed and sped up will be in accordance to the ratio of the relative masses.  Say we're talking 10,000:1, the black hole will decelerated one 10,000th of a way toward the inertial frame of the planet.

I think it's safe to say that if you're talking about normal, naturally forming black holes, a planet doesn't have the mass to stop it.