# Thread: What if a mini blackhole hits the Sun?

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## What if a mini blackhole hits the Sun?

Hi!

I'm reading the excellent Isaac Asimov's "A choice of catastrophes" and I'm curious about a "mental exercise" (call it crazy fantasy, I don't care, it's fun and I have fun doing it, you should try it): "what if" a mini black hole (mass of an iceberg) "hit" the Sun? If it hits at a certain angle and velocity, it can be trapped by Sun gravity and goes to the core, and starts to devour our closest star. How long it will take to the Sun suffer it's own "big bang"?

In the core of the Sun, mass will be pushed to the mini blackhole (mbh, for short) by the pressure of the core, I'm right? So you have big pressure sending lots of matter into a small drain. Until some time has passed and some mass had absorbed, there's only the pressure. After certain time, the mass of the mbh is enought to accelerate mass by itself. More time, and the gravitational pull will be stronger than the pressure push, and sooner we will have X-Rays being emmited by matter that "falls" into de mbh (still a mini?). More time and the Sun "blows".

Is that a plausible scenery (forget about the extremely low probability of a mbh already hitting the Sun)? How long such catastrophe will take until the last act?

[]s

2. I'm not really sure what would happen. A mbh with the mass of an ice burg would have a Schwartschild radius of a few ~75-150 microns. About the size of a virus maybe? I think the radiance at the photosphere of the Sun would blow it back into space or possibly it'd just float there at the surface gathering mass until it can sink to the center of the Sun.

Now that I think about it, a mbh that small might evaporate from Hawking radiation before it could "eat" the Sun.

3. Assuming this mini black hole isn't captured by the sun, it would pass through it, collect any matter it collides with, and continue on its merry way along a new trajectory.

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Originally Posted by Kristophe
Assuming this mini black hole isn't captured by the sun, it would pass through it, collect any matter it collides with, and continue on its merry way along a new trajectory.
I disagree. Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. The mbh would behave about the same as an iceberg would (except for the melting and other effects relating to the size difference. I agree with Russ and think the bh would stay in the Sun until it evaporates due to Hawking Radiation.

Concerning Russ' post about the radiance of the Photosphere, what would be the mechanism that accelerates the mbh? Assume a proton or something enters the mbh's event horizon. Presumably the particle will bounce around inside the bh, but of course none of the particles will leave the event horizon. If this behavior causes the center of mass to move, then would this be considered information coming out of the bh? IIRC, the only things you can know about a black hole is its mass and its rotation, Hawking's recent announcement on the subject notwistanding.

In the same way, a photon entering the bh would add momentum to the system.

5. actually the sun would stay with the blackhole till it got sucked into it. A blackhole is a blackhole.

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Originally Posted by jfribrg
Originally Posted by Kristophe
Assuming this mini black hole isn't captured by the sun, it would pass through it, collect any matter it collides with, and continue on its merry way along a new trajectory.
Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. .
This statement means nothing. Mass does not overcome gravity. Earth (or the sun) doesn't have an escape mass, it has an escape velocity.

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I disagree. Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. The mbh would behave about the same as an iceberg would (except for the melting and other effects relating to the size difference. I agree with Russ and think the bh would stay in the Sun until it evaporates due to Hawking Radiation.
Unless the black hole was part of the initial formation of the solar system it will have entered the system on a hyperbolic orbit. This means it will have an incoming velocity towards the sun greater than system escape velocity. It would pass through the sun as if it weren't there and keep right on going with a possible change in trajectory.

Such an object is so small in relation to the mass of the sun that it can be treated as a restricted case of the two body problem where one body has negligeble mass. This is relatively trivial to solve. There might be some unpredictable effects caused by the fact that a black hole has electric charge as one of its properties. This would interact with solar magnetic fields.

8. An iceberg is a bit of a vague measure, since a large berg could be bigger than Yorkshire; but a billion tonne iceberg is perfectly possible, so let's go with that.
A black hole with that mass (a billion tonnes) would last two trillion years, so could easily have been created in the Big Bang and still be around.
It would be very small though; about ten times the diameter of a proton.
(see Jim Wisniewski's Black Hole calculator here)

This is actually quite big enough to absorb protons from the Sun's core plasma, if it's hyperbolic orbit passes through that region; this interaction will act as a drag on the hole, and will change the orbit somewhat.
In the worst case, it might change the hyperbolic orbit into an elliptical orbit; the hole would come shooting out of the Sun, at a slower velocity than it went in; loop round the Solar system once (probably taking a number of years to do this) then plunge back in.
And be slowed down some more.
After a few passes through the Sun the aphelion of the black hole's orbit will be below the surface of our star; it's fate will then be sealed. But even then it will take a long time for a small black hole to absorb such a large object.
(don't know how long though; this is a more complex problem, beyond the range of Jim's excellent calculator)

9. Originally Posted by Evan
I disagree. Something as small a mass as an iceberg would not be able to overcome the gravitational pull of the Sun. The mbh would behave about the same as an iceberg would (except for the melting and other effects relating to the size difference. I agree with Russ and think the bh would stay in the Sun until it evaporates due to Hawking Radiation.
Unless the black hole was part of the initial formation of the solar system it will have entered the system on a hyperbolic orbit. This means it will have an incoming velocity towards the sun greater than system escape velocity. It would pass through the sun as if it weren't there and keep right on going with a possible change in trajectory.
I canīt see how a mbh could form in the vicinity (10 ly at least) of our solar system. If it wasnīt from the original solar system material, then it should have probably formed far away, a long time ago. Something like that wouldnīt have the time to reach the solar system. As Russ says, it would evaporate very fast, due to its small size.

10. Originally Posted by kenneth rodman
actually the sun would stay with the blackhole till it got sucked into it. A blackhole is a blackhole.
[nitpick]Black holes don't suck[/nitpick]

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I wasn't proposing it formed as part of our system, just that that is the only way it wouldn't be on a hyperbolic orbit with better than escape velocity. Escape velocity at the sun's surface is 617 kps. It is reasonable to assume that such an object would be coming in with a terminal velocity of perhaps 1000kps at the sun. If it passed through the sun core it would transit in 23 minutes and the core in a few minutes. I wouldn't expect much slowing even if it did interact. The momentum of such an object is a rather large number at that velocity. The density of the core is perhaps ten time that of lead while the black hole may be considered to have nearly infinite density. From what I have read the suns core would have much the same effect as passing through a thin gas, which is to say none at all.

12. Yes, that is true; scooping up a few protons isn't going to change the orbit of a billion tonne black hole very much. So the most likely outcome by a very long way is that the hole comes back out of the Sun into interstellar space.

It might happen all the time and we would be none the wiser.

13. 1/ Several posts above refer to Hawking radiation (HR) terminating the BH. That radiation occurs in inverse proportion to the mass of the BH and its consequent radius - or rather that of its event horizon - so that the smaller the Hole, the faster it loses mass from HR. But that assumes the BH is in empty space - this one will also be gaining mass as it captures matter through the EH, and that will be increasing as the cube of its mass.

Can anyone say if the capture rate or the HR mass loss rate will win for a Gtonne BH in the heart of the Sun? If HR wins, how big must the BH be for it to lose and inexorably gain mass?

2/ Someone referred to a proton, bouncing around within the EH. We cannot (by definition) know what happens, but surely even a subatomic particle would be torn apart by tidal forces so that it is reduced to its component quarks, strings or whatever underlies them?
And bouncing around? The EH isn't a shell or a membrane. It is a zone, beyond which we know not, but we can assume that any particle that enters must continue it's descent towards the discontinuity.

3/ Read "The Hole Man" by Larry Niven. A miniBH will 'eat' Mars in something between months and years, not millenia. "The math is chancy...." As it was his speciality I suppose that Niven may have been advised by Robert Forward in that estimate, so however chancy that timing may be accurate.

John

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The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.

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The way I see it an atomic scale black hole would basically drill an atom sized hole through the sun in the few minutes it would take to pass through. That doesn't amount to very much matter even if it ate it all.

The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.

16. Originally Posted by bigsplit
The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.
Yeah, I'm with Evan on this one.

A) How do you fill a black hole? Adding mass to a black hole increases its event horizon.

B) What would it become?

C) If we assume the black hole to be a frictionless sphere (someone laugh, darn-it!), then it's clear that the only forces affecting it would be the sun's gravity, and the change in momentum due to the absorption of protons. Since proton motion in the sun is random, the net change in direction of the black hole due to interactions with protons (assuming the black hole to be electrically neutral, for fun) would be due entirely to the gravity of the sun. So, why is it stopping?

17. A BLACKHOLE is a BLACKHOLE. Its mass is so great that light itself is trapped by its gravitation strength. However small in size its event horizon is; it still has massive amount of gravitational strength beyound its event horizon. Now im aware that in principle there is no limit to how much or how little mass a black hole can have. Any amount of mass at all can in principle be made to form a black hole if you compress it to a high enough density.
The crux of the matter is that the only way i know of that a blackhole is naturally created is the colapse of a star with sufficient mass that the gravitational force is great enough to trap light. that mass is alot greater then the mass of our star; It is why I beleive our star would be doomed. This senario, though thank god its unlikely, is still a possiblity. If your stating that a Mini blackholes mass is being compressed by something other than its own gravity(an artificially created blackhole) then i suppose it would all depend on its velocity. if it was traveling fastenough it would pass right through our star with no ill effects, it could become trapped into an oliptical orbit around our sun, or it could get sucked into the sun itself. the sun In this case would still be fine because some force other than gravity is compressing this mini blackhole. I know im in effect doing a 180 on my original answer but i was thinking of a naturally occuring blackhole.

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See here.

19. Originally Posted by kenneth rodman
if it was traveling fastenough it would pass right through our star with no ill effects, it could become trapped into an oliptical orbit around our sun, or it could get sucked into the sun itself.
I think that if the mini BH (or primordial BH) were coming in from the interstellar space, it would be traveling, say, at some 200 km/s (maybe more). It would take 2 hours to traverse the Sun. It seems to me that it wouldnīt experience any "drag" from the plasma (somebody correct me if Iīm wrong), so it wouldnīt decelerate. In fact it would still be accelerating inside the Sun, heading to the core. Once inside the Sun, due to the bhīs high speed, the particles wouldnīt have the time to "orbit" it prior to falling inside the EH (bhīs donīt suck). Only the matter right ahead on its trajectory would be possibly captured, a negligible amount. It would cross the sun like a red-hot needle punching a chunk of butter, and emerge on the other side with its hyperbolic orbit unaltered.

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think that if the mini BH (or primordial BH) were coming in from the interstellar space, it would be traveling, say, at some 200 km/s (maybe more).
Uh, no. The escape velocity of the Sun from the surface of the Sun is 617 kilometers per second. This means that if an object were placed at rest an infinite distance away (warning: though experiment!) that it would accelerate to 617 kps by the time it encountered the surface of the Sun. That is the minimum that an extrasolar object would accelerate to.

This velocity would be added to any already existing relative velocity the object has. It is reasonable to assume a few hundred kps intrinsic velocity that would be added to the 617 kps escape velocity of the Sun. So, the object would end up traveling at 1000 or so kps by the time it entered the Sun. It could easily be faster if it were extragalactic as the escape velocity of the Milky Way exceeds 1000 kps.

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http://library.thinkquest.org/C00757...ance/core6.htm

CesarAKG postulated a mbh with the mass of an iceberg. Just for fun I assumed an iceberg 100 meters on a side (mass = 10**9 kg) and used the equations on the indicated link. Such a mbh would have an enormous temperature and be radiating an incredibly large amount of gamma radiation. I'm not sure it would absorb mass with that much photon flux pushing out of it. The collision would be spectacular, however.

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Originally Posted by JohnD
1/ Several posts above refer to Hawking radiation (HR) terminating the BH. That radiation occurs in inverse proportion to the mass of the BH and its consequent radius - or rather that of its event horizon - so that the smaller the Hole, the faster it loses mass from HR. But that assumes the BH is in empty space - this one will also be gaining mass as it captures matter through the EH, and that will be increasing as the cube of its mass.
John
A black hole the mass of an iceberg could form in the center of the sun and still radiate so much energy via Hawking Radiation that it would cease to exist.

A black hole the mass of an asteroid (few billion tons) would have a "temperature" of tens of millions degrees and would basically "explode" since it would convert all it's mass into Hawking Radiation.

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So postulate a MBH one thousand times more massive. The size grows to one tenth the size of a hydrogen atom and the luminosity falls to 356 watts. More important is that at a radius of a millimeter or so the gravity is less than one G. Inverse square law really kicks into gear when dealing with such a small object.

24. Originally Posted by wedgebert
A black hole the mass of an asteroid (few billion tons) would have a "temperature" of tens of millions degrees and would basically "explode" since it would convert all it's mass into Hawking Radiation.
Nope;
that is why I included the link to
Jim Wisniewski's Black Hole calculator here;
http://xaonon.dyndns.org/hawking/

a billion tonne black hole would have a temperature of a hundred billion degrees, but has such a smal radiating surface that it would last 8.4e19 seconds, which is a few hundred times the age of the universe.

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Have any sol stelar mass black hole candidates been discovered? It would seem if this were worth postulation you would need to find black hole candidates that have unusually small mass.

26. Originally Posted by Evan
Uh, no. The escape velocity of the Sun from the surface of the Sun is 617 kilometers per second. This means that if an object were placed at rest an infinite distance away (warning: though experiment!) that it would accelerate to 617 kps by the time it encountered the surface of the Sun. That is the minimum that an extrasolar object would accelerate to.
A thousand pardons.

Unforgivably, I didnīt take the Sunīs escape velocity into account while elaborating my post. I simply put out an abstract idea. Anyway, the core of the reasoning remains intact: it wouldnīt be trapped by the Sun. Thanks for pointing it.

Edited for style.

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Interesting that the mbh might not be slowed by the sun at all. Let's kick it up another notch: a mbh in orbit around the galaxy is sped up by its passage near the sun, as a gravitational slingshot.

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Originally Posted by Kristophe
Originally Posted by bigsplit
The mbh would be instantly filled with ordinary matter if it fell into the sun, there would probable be some minor fireworks, but it would most definately not remain a black hole and it most certainly would not escape.
Yeah, I'm with Evan on this one.

A) How do you fill a black hole? Adding mass to a black hole increases its event horizon.

B) What would it become?

C) If we assume the black hole to be a frictionless sphere (someone laugh, darn-it!), then it's clear that the only forces affecting it would be the sun's gravity, and the change in momentum due to the absorption of protons. Since proton motion in the sun is random, the net change in direction of the black hole due to interactions with protons (assuming the black hole to be electrically neutral, for fun) would be due entirely to the gravity of the sun. So, why is it stopping?

Once the mini black hole made contact with the Sun there would be some devastating effects. Since the matter falling into the BH has less density and the BH gravity well would be "polluted" with too large of particles for it to digest. Essentually, the MBH would be absorbed by the sun, or if you prefer, the inverse.

If the BH were bigger, would our sun simple pass through or bounce off the Sun. No, I don't think so. The gigantic sun would eat that MBH up and digest it. Whether it burps it out or just puts on a few pounds, I am not sure. I don't think it would vomit it right back out.

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Once the mini black hole made contact with the Sun there would be some devastating effects. Since the matter falling into the BH has less density and the BH gravity well would be "polluted" with too large of particles for it to digest. Essentually, the MBH would be absorbed by the sun, or if you prefer, the inverse.
That just doesn't make any sense.

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I don't believe there is such a thing as "too large a particle" or in a nother translation "too many particles" for a black hole to digest. The particle in question could be larger than the schwarzschild radius of the black hole, but as soon part of it crosses the event horizion, it's still going to be "sucked" in and torn apart. If there's too many particles, well the black hole doesn't care, they'll all end up occupying the same point in spacetime that we call a singularlity.

If you discount Hawking radiation (otherwise the mbh wouldn't exist for more than a very brief moment), if the mbh passes near the sun and doesn't reach escape velocity on the inbound leg, the sun is more than likely doomed. The only way for the sun to escape the mbh would be for the decaying orbit of the mbh to be so large that the sun continues it's normal life before the mbh is finally "caught".

If the mbh passes though the sun, it would absorb everything inside its swhwarzschild radius. As it does it will gain mass, increasing the SC radius, and there for absorbing more.

If the mbh has acheived escape velocity, then it will go about it's merry way. If it hasn't, it will eventually fall back into the sun. Once it does, this process will continue at an ever increasing rate until the sun is gone. Once that happens, life in the rest of the solar system will get quite dark and chilly, but otherwise continue on as normal.

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