An interesting thought... blowing up a black hole?

[Meldread]

I was reading a story in New Scientist about exotic stars that may mimic the big bang. Suddenly, a question popped into my head.... could it be possible to blow up a black hole? We know what happens when anti-matter and matter touch each other... so imagine a star-sized object (with equivalent mass) made entirely of anti-matter. Then the anti-matter star crosses paths with a black hole.... what happens to the black hole? I assume the black hole - at least at its singularity - is made up of matter.

I have no idea what would happen, but I'm certain it would be one of the most awesome events to watch.

[Walk away]

Count me in!

I'll bring the hot dog buns and the cole slaw!

[Gman2]

1. Dangle a world, in the hole opening, with a long extension cord, voila.

[krispos42]

2. trillions of tons of matter reacting with trillions of tons of anti-matter...

...all times the speed of light squared.

Yikes.

[Meldread]

4. Yes, I know... which is why it's an interesting question to consider!

Would the explosion literally rip open the black hole destroying it? Would nothing happen (the explosion happening WITHIN the black hole itself at the singularity)? If the black hole exploded could the force be so strong as to rip a hole in the universe itself?

What if the force was so powerful as to create another big bang within our universe - a universe within a universe - so to speak - both expanding outward faster than the speed of light?

[GreenStormCloud]

8. Anti-matter does not have anti-gravity, it has gravity.

The black hole pulls on your anti-matter object, and it pulls on the black hole. At the singularity, there is only gravity and the memory of mass. All that happens is that the black hole gets a bit larger.

[sui generis]

6. sounds like the last time I had red onions in my salad.

:blush:

[TheWraith]

9. One stellar mass of antimatter reacting with matter would be, roughly speaking...

...the equivalent of 85,503,951,600,000,000,000,000 exatons of TNT. To compare, that's about as much energy as all the stars in this galaxy put out over the course of nine thousand years.

[Occulus]

23. Good GOD.

What would happen to a galaxy in which that event occurred? Also, not that I don't believe you, but how did you arrive at that particular number?

[TheWraith]

31. At first, very little would happen to that galaxy...

However, that's only because the energetic effects would be propagating at sublight speed. So for instance, it would be probably 30,000 years or so before we noticed it had happened, Earth being a good ways out from the galactic core. Other places wouldn't see the effects for 50,000 years or more.

That said, once the wave-front passed an area, the galaxy that previously existed there would probably cease to exist in any meaningful form. Any star or planet which wasn't close enough to the core to be vaporized outright would be cooked to the point of being debris. It would probably be in effect a miniature big bang of expanding death.

As to the number... if we're talking about one stellar mass, that's 4.384 times ten to the thirtieth pounds. One pound of antimatter releasing it's energy with one pound of matter produces the equivalent energy of 19.5 megatons of TNT.

http://www.edwardmuller.com/right17.htm

Multiply those together. From there, it's math to break that huge number up into the slightly more manageable figure of exatons, which is a thousand billion billion. An exaton is equivalent to about the total energy output of the sun for ten seconds. There's between 200 and 400 billion stars in this galaxy, so figuring for an average of 300 billion, that's enough exatons to equal those 300 billion stars for about 9,000 years of output.

[ThomThom]

53. yes the "big bang"

When the last black hole eats the second to last black hole we get a big bang and it all starts again.
Just my thoughts.

[jgraz]

3. Nope, the black hole would eat the star without a burp

Remember, matter and anti-matter combine to create photons, which are also trapped by a black hole. Even if there were a large amount of matter lurking just inside the event horizon, the resulting explosion of photons would just spin into the singularity like everything else.

Of course, from our point of view, time would stop for the star as it crossed the event horizon, so it would never quite make it inside the black hole within the lifetime of the universe.


But... Hawking has shown that all black holes will eventually explode. Quantum vacuum fluctuations cause them to leak hawking radiation (one virtual particle goes in, the other escapes), eventually leading to their complete evaporation. The speed of evaporation is inversely proportional to the surface area of the event horizon. So, as a black hole gets smaller, it will eventually explode in a shower of virtual particles.


Edit: The "no burp" isn't really true. The star itself would emit a flood of x-rays as the tidal forces ripped it apart and heated its gas to millions of degrees. About 40% of its mass will be either radiated away or ejected in twin jets of relativistic particles.

[Meldread]

5. Awww...

...that's no fun. :P

[jgraz]

7. Actually, it's a lot of fun. Few things are more brain-bending than black holes.

If you can find it (or afford it) I highly recommend Alex Fillippenko's 12-part lecture series on Black Holes. http://www.teach12.com/ttcx/CourseDescLong2.aspx?cid=1841

[Meldread]

I didn't mean black holes weren't fun...

...just that the fact that it wouldn't explode wasn't fun. :P Thanks for the link, though.

But... to try and move things back on track. Assuming there was some way that we could cause a black hole to explode... what would happen? Let's assume the black hole that explodes is the super massive black hole in the center of some giant galaxy - let's say Andromeda or the Milky Way.

How would space and time react to the sudden destruction of a black hole? Starting from within the event horizon, expanding outward to the nearest stars, all the way to the edges of the galaxy.

[jgraz]

17. You're really talking about the annihilation of a large amount of matter

There's nothing special about a black hole in terms of a collection of mass. They are just extremely dense collections of mass, but no heavier than any other collection. If the sun turned into a black hole, the earth's orbit would continue as normal (though the lack of light would suck for us).

Conversion of a black hole to radiation would have no effect on space and time, other than removing the local gravity well as the photons dispersed. No energy would be created in this process (as mass and energy are equivalent), so the general curvature of space and time would remain the same.

That having been said, the conversion of a black hole of 1 billion solar masses directly to radiation in one second would yield approximately 8.9x10⁵⁵ watts. This would exceed the power output of all galaxies in the observable universe by a factor of 500,000.

Is that a big enough BOOM for ya? :P

[Fumesucker]

10. Why could there not be antimatter black holes?

Not that there would be any way to find out if they were matter or antimatter since the only determinable properties of black holes are mass, charge and angular momentum and AFAIK antimatter does not differ from regular matter in those properties.

[jgraz]

13. Black holes are neither matter nor antimatter

They're a singularity (a point of theoretically infinite density) surrounded by an event horizon.

[Fumesucker]

14. True, but a black hole could be formed by either matter or antimatter..

Which was what I meant, my phrasing was poor.

[jgraz]

19. Yep. Theoretically, you could form one by squeezing enough photons into a small space

Which is what they hope to do with the Large Hadron Collider.

[Laura902]

11. The anti-matter would go towards the black hole and be sucked in

not even light can escape from a black hole. When the big bang first happened it is theorized that all the matter that exploded was in a ball so dense that 1 teaspoon of it would be heavier than the Himalayan mountain range, so it would seem that black holes can teach us much about how this event happened.

[StarfarerBill]

12. The antimatter will react with the matter being pulled in, even if it's only atoms and/or molecules.

Something should happen; whether it would be awesome would depend on the amount of matter with which the antimatter has to react.

A black hole is a gravitational phenomenon, right? Therefore, its only effect, sans incoming matter, on the antimatter mass would be to tear it apart and crush it in the hole's gravitational tides...or so I would think. Still, a helluva lot of energy would be released, regardless.

[Fumesucker]

15. A lot of energy get released by normal matter entering a black hole..

Since the matter entering a black hole almost always has some angular momentum the matter almost never goes straight into the black hole but rather spirals around it like water around a drain. The resulting friction of the matter in the vortex (known as an "accretion disk") heats it to very high temperatures which gives off a great deal of radiation.

http://en.wikipedia.org/wiki/Accretion_disc

An accretion disc is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a central body. The central body is typically a young star, a protostar, a white dwarf, a neutron star, or a black hole. Gravity causes material in the disc to spiral inward towards the central body. Gravitational forces compress the material causing the emission of electromagnetic radiation. The frequency range of that radiation depends on the central object. Accretion discs of young stars and protostars radiate in the infrared; those around neutron stars and black holes in the x-ray part of the spectrum.

[StarfarerBill]

16. Thanks for the clarification.

But my first point was that the magnitude of a matter/antimatter reaction would depend on the amount of matter with which it had to react, right? Even a stellar-mass of antimatter wouldn't make a big boom if it only had atoms or molecules of matter to react with, would it? That is, if the black hole had eaten all large matter masses previously; if not, then the antimatter would still have a lot to react with. :)

And I think my second point agrees with your explanation: the antimatter being torn apart and crushed by the black hole's gravitational tides would cause the AM mass to release a lot of energy.

[Fumesucker]

18. Right, 100% antimatter would act just like normal matter in an accretion disk..

For most purposes anyway..

The antimatter-matter reaction is limited by the smaller amount, be it of either flavor.

[StarfarerBill]

20. Cool; we agree.

:thumbsup:

[Occulus]

21. So after reading this exchange, we've arrived at a matter/antimatter singularity collision?

With the mass of stars, no less, not a microsingularity.

That would be one spectacular explosion. One question: given that matter and antimatter annihilate each other, how would an antimatter singularity of appreciable mass form in the first place? Wouldn't it almost have to exist outside the universe for it to exist at all?

[StarfarerBill]

22. Um, what collision?

As I understand it, a singularity is not matter, but a point of infinite gravitational density; while ripping up and crushing an antimatter mass would cause that mass to release a lot of energy, there's nothing there, where the singularity is concerned, with which to collide. In other words, the AM mass would be shredded, smashed, and eaten, just like regular matter would be.

I'm definitely no astrophysicist or cosmologist, so please correct me if I'm wrong here.

[Occulus]

25. Blowing up a black hole, like the OP said. I thought you were talking about

a black hole (the accretion disc of one, if you prefer) and what might happen if it hit one made of antimatter, but if I understand you correctly, it wouldn't make any difference.

Do we have any real examples of two 'normal' black holes colliding?

[StarfarerBill]

26. To be honest, I don't know that it's possible to blow up a black hole.

I've read that they'll evaporate or collapse in on themselves from lack of incoming matter, but I think a singularity is proof against even a stellar-sized antimatter mass.

Now, if the accretion disk has lots of matter in it, then yes, all that matter and antimatter reacting would be quite spectacular. :)

Hmmmm...I seem to remember reading about what would happen if two black holes collided, but I think all that would happen would be that the larger would consume the smaller and take the former's mass into itself...along with a hellacious release of energy.

[jgraz]

27. Here y'go

http://www.youtube.com/watch?v=GAwO1okR074

Two black holes merging.

[StarfarerBill]

28. Cool! Thanks! :)

So as I understand this, two black holes of equal mass simply merge into one another, creating a larger black hole? Besides an increase in gravitational waves during the merging, wouldn't energy (Hawking radiation?) also be released as it normally is with a hole in its normal state, only more so?

As I said earlier, no astrophysicist or cosmologist here, so feel free to push back my ignorance with knowledge. :)

[jgraz]

29. Hawking radiation is only related to the surface area of the event horizon

Nothing that happens to a black hole will affect its temperature (rate of hawking emission) other than a change in the size of the event horizon. The smaller the horizon, the more quickly it evaporates. As such, the merging of two black holes will result in a *reduction* of hawking radiation.

[StarfarerBill]

30. Ah, another clarification! Thanks again. :)

But I don't quite understand how the merging of two equal singularities would result in a reduction of Hawking radiation; wouldn't the merging increase the size as well as the mass of the black hole, its event horizon, and thus the radiation?

[jgraz]

32. The total radiation from both BHs would be reduced

A black hole's luminosity (amount of Hawking radiation) is inversely proportional to the square of its mass. A black hole of 1 solar mass has a luminosity of 8.998363e-29 watts. A black hole of 2 solar masses has a luminosity of 2.249591e-29, or 1/4th that of a 1-solar-mass BH. Combine two black holes and the resulting Hawking radiation will be far less than the original luminosity of both objects.

Here's a handy calculator if you want to see how it works: http://physics.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=physics&cdn=education&tm=8&f=00&tt=12&bt=1&bts=1&zu=http%3A//xaonon.dyndns.org/hawking

[StarfarerBill]

33. I'll admit, the math is far beyond me, so I'll take your word for it.

Can the reason why smaller black holes radiate more than larger ones be explained without equations, for an utter layman like me?

[Meldread]

34. I suck at this, but I'll try and explain from my understanding.

I'm a layman like you, but I find science interesting and try and keep informed as best I am able with limited comprehension.

When it comes to Hawking Radiation and Black Holes... try to picture it similar to evaporation. If you place a pot of water on a really hot surface such as a stove, it'll take awhile for the water to boil away. But let's say you take a drop, and place it on a hot surface it is going to boil away almost instantly.

It's similar for Black Holes. This is why a micro black hole can be formed on Earth, but it "evaporates" virtually instantly - like the drop of water.

[StarfarerBill]

36. So we're in the same boat, so to speak. :)

Thanks for the explanation.

So you're saying that a smaller black hole evaporates more quickly, thus releasing more Hawking radiation? Okay, that makes sense. But if I understand your metaphor, steam is the radiation, right? Yet, a pot of boiling water puts out a lot more steam than a drop of that same water; so is the metaphor still applicable (I ask because it helps to picture the process more concretely in my mind)?

[Meldread]

37. I think "more" is used relatively.

It is somewhat hard to visualize due to the time scales. A micro black hole vanishes virtually as soon as it appears. It produces LESS radiation throughout its life than a super massive black hole at the center of a galaxy, but it releases all of its Hawking Radiation immediately. Therefore, relative to the super massive black hole it releases more radiation.

I could totally be off base (and I probably am)... the more I try to explain it, the less certain I feel about my answer. :P

But that is always how I tried to envision Hawking Radiation - as water evaporating.

[jgraz]

38. It actually is the weirder interpretation

The smaller the black hole, the more luminous it is. Now, luminosity is a function of light emitted over time. A micro black hole may emit relatively few particles, but it does so in almost the shortest time possible, thus making it more luminous than the black holes at the centers of galaxies.

[StarfarerBill]

41. That's the way Meldread explained it to me, and in terms this layman could understand.

Thanks to you both! :)

[StarfarerBill]

40. You're probably right; that's the logical way to look at it.

Have you read the earlier posts to this thread by jgraz? They say:
"Hawking radiation is only related to the surface area of the event horizon. Nothing that happens to a black hole will affect its temperature (rate of hawking emission) other than a change in the size of the event horizon. The smaller the horizon, the more quickly it evaporates. As such, the merging of two black holes will result in a *reduction* of hawking radiation."

And in the next post:
"A black hole's luminosity (amount of Hawking radiation) is inversely proportional to the square of its mass. A black hole of 1 solar mass has a luminosity of 8.998363e-29 watts. A black hole of 2 solar masses has a luminosity of 2.249591e-29, or 1/4th that of a 1-solar-mass BH. Combine two black holes and the resulting Hawking radiation will be far less than the original luminosity of both objects."

If I'm understanding this correctly, it sounds like what you related with the boiling-water analogy. So unless I learn differently later, your analogy will be how I understand how smaller black holes can emit more Hawking radiation than larger ones.

Thanks for all your help, and for your original post; my brain hasn't had this hard a workout in a long time! :)

[jgraz]

42. Here's the problem with the boiling water analogy

A boiling pot will emit more steam per second than a sputtering drop. A galactic size black hole will emit fewer particles per second than a micro black hole. In absolute terms.

[TheMadMonk]

48. I'll have a go. Theory has it that empty space constantly spawns...

...matter-anitmatter pairs of particles, which then within the limits of Heisenberg's Uncertainty Principle anhilate each other before the universe can notice this temporarly violation of the Law of Coservation of Mass-Energy. Larger (higher energy) particle pairs can exist for shorter periods of time than smaller (low energy). These are called "Virtual particles".

This has actually been demonstrated experimentally by placing two plates an infintesmal distance apart, thus excluding the posibility of M-AM pairs of certain energy levels from forming (there isn't enough room). Thus the "empty" universe outside where these "missing" pairs can still form, exerts a small but measurable force pushing the two plates together. This is called the Cassmir Force.

Now, it is possible for these pairs to form just outside the event horizon of a black hole and if conditions are exactly right, one of the pairs can be gobbled up by the black hole BEFORE it has a chance to recombine with its partner and suddenly a "virtual" particle becomes "real". As would the violation of the Law of Conservation of Mass energy if the "Auditors of Reality" didn't ballance the books by crediting the black hole with negative mass.

A large black hole has a relatively flat "surface" and thus there is a considerable chance that the suddenly "real" particle will "fall" below it and "rejoin" it's partner. The books stay ballanced, because the temporarily "real" particle's positive mass, ballances the negative mass gain of the black hole and everything cancels.

A teeny tiny black hole on the other hand has physical dimensions much closer to the distance that each member of a virtual particle pair can cover in the time that they are "allowed" to exist before the universe "notices" their existance and "causes" them to recombine. If one of such a pair gets gobbled up there is a much higher chance that it's partner will "miss" the black hole and fly off into the universe at large. The smaller the black hole the greater the chance. Until we get down to gigaton mass black holes which will evaporate in a flash of gamma radiation in a fraction of a second.

[damntexdem]

24. I doubt anyone knows what happens in a black hole, whether matter/antimatter matter.

But if there were an explosion, presumably the products would not escape, because they could not exceed the speed of light. And to watch the awesome event, one would have to be inside the event horizon -- but by then, one would be dead.

[Fumesucker]

35. That depends on the size of the mass of the black hole and the size of the event horizon..

The event horizon isn't an actual physical thing, just the location beyond which the escape velocity exceeds that of light, given a sufficiently massive black hole the event horizon is so large that tidal effects are not dangerous at that radius from the singularity, a living human could pass through it and never notice the transition.

[jgraz]

39. BTW, thanks for this post!

It's the most fun I've had on DU for a while. :hi:

[krispos42]

43. I just realized... I don't think black holes can be antimatter.

They're made from neutron matter, which is made entirely from neutrons. The neutrons are formed when the electrons (or anti-electrons) are forced into contact with protons (or anti-protons), neutralizing the charges and forming neutrons.

So you'd just have two black holes colliding into one bigger black hole... plus some sort of massive fireworks display.

[jgraz]

44. If you had a star made from antimatter, it would collapse to an antineutron star

http://en.wikipedia.org/wiki/Antineutron

Of course, there's no requirement that a black hole only be created from a collapsing neutron star. Any concentration of mass inside the Schwartzchild Radius will be a black hole -- even photons.

[krispos42]

45. Hmph, I was not aware of that

So an antineutron and a neutron will still annihilate each other?

[jgraz]

47. Yep. All it takes is for the quantum numbers of both particles to sum to zero.

Electrical charge is only one such http://en.wikipedia.org/wiki/Quantum_number">quantum number.

[tinrobot]

49. There are such things as antineutrons

And they would interact with matter in the same way antiprotons or antielectrons interact - explosively.

But black holes are not made of neutrons. That would be a neutron star, which is the last step matter can take before collapsing into a black hole. When a neutron star exceeds 8 solar masses, gravity exceeds the weak nuclear force and the neutrons collapse into each other with no forces left to hold the matter apart - thus forming a black hole.

[goodboy]

46. Reminds me of the new Star Trek movie. Something like that happens at the end. (nt)

[Orsino]

50. The escape velocity would still be greater than that of light...

...so nothing is going to escape that final plunge into the black hole.

There would be some impressive fireworks beforehand, as the antimass is ripped apart by tidal forces and undergoes mutual annihilation with ordinary matter along the way.

[booley]

51. Doesn't time slow down near a black hole?

So even if you do get the trillions of tonnes of anti-matter and somehow threw it into the black hole, would't it still take billions if not trillions of years before you would even get a clue that it had an effect?

[caraher]

52. Yes, and no

Time "slows down" in the sense that if you tossed a clock in and could record (from a safe distance) the "ticks" as it fell, the ticks would come at longer and longer intervals as measured from outside. But the clock itself would merrily accelerate into the black hole, be ripped apart by tidal forces and disappear into the event horizon quite quickly as seen by us.

[RagAss]

54. This....