Blackholes: Accretion Vs Expulsion

[neufer]

IMO, even a 1 solar mass BH would cause the whole back end (if not first the whole front end) of the Sun to explode as about a million years of stored up photons in the Sun's radiative zone now encounter protons that are suddenly in free-fall (if only for a couple of minutes).

<<The radiative zone is just beyond the core of the Sun. It gets its name from its primary method of heat transfer: the radiation of light. As our photon leaves the core and enters the radiative zone, it encounters an obstacle: densely packed protons. They are so crammed together, photons can’t travel more than a few millimeters without hitting another one. Each time one does, it loses some of its energy and is scattered in a random direction. It can take anywhere from a few thousand to a few million years for one photon to escape. It’s not just the light from distant stars that takes millions of years to reach us; the light from our own Sun does too!>>

[BDanielMayfield]

A little more on the oscillations the Sun might experience after the main event. I wouldn't think that the poles would pulsate up and down much after the BH, but the whole Sun could go into a variable phase while it hunts for balance and stability. All stable, constant brightness stars have an internal balance between gravitational contraction and heat from fusion in the core. But in this scenario the balance has just been upset horribly. As the BH leaves even though the sun has lost mass it should have gained a lot of internal heat, causing the Sun to puff up, like Red Giants do. But then the core cools below the fusion threshold and it will shrink, until compressional heating kicks off fusion again, causing expansion, contraction ... It could take a long time for this to settle out.

It could. Or, the actual disruption might be minimal and little mass lost. Or, the fusion could stop and restart again in one oscillation cycle lasting just a few hours.

You've convinced me that actual accretion during the transit phase would be small due to conservation of angular momentum, but as Art pointed out an accretion disk many times more massive than what falls into the hole could be 'torn away with it'. That sounds like a likely possibly.

On the one hand, all this uncertainty allows the author a fair degree of flexibility. On the other, it means there's a good chance that any proposed scenario will be wrong, and possibly demonstrated to be so not long after publication.

But when has that deterred sci-fi authors? They pretty much all get it wrong.

Bruce

[BDanielMayfield]

IMO, even a 1 solar mass BH would cause the whole back end (if not first the whole front end) of the Sun to explode as about a million years of stored up photons in the Sun's radiative zone now encounter protons that are suddenly in free-fall (if only for a couple of minutes).

<<The radiative zone is just beyond the core of the Sun. It gets its name from its primary method of heat transfer: the radiation of light. As our photon leaves the core and enters the radiative zone, it encounters an obstacle: densely packed protons. They are so crammed together, photons can’t travel more than a few millimeters without hitting another one. Each time one does, it loses some of its energy and is scattered in a random direction. It can take anywhere from a few thousand to a few million years for one photon to escape. It’s not just the light from distant stars that takes millions of years to reach us; the light from our own Sun does too!>>

It's very good for us that we're not irradiated with gamma ray photons from the Sun's core. Indeed, this energy needs to be throttled back greatly or life on Earth wouldn't be possible.

So is something like a Supernova the most likely outcome Art?

Bruce

[Chris Peterson]

On the one hand, all this uncertainty allows the author a fair degree of flexibility. On the other, it means there's a good chance that any proposed scenario will be wrong, and possibly demonstrated to be so not long after publication.

But when has that deterred sci-fi authors? They pretty much all get it wrong.

No, I think there's quite a bit of science fiction that has held up well to advancing scientific knowledge.

[neufer]

IMO, even a 1 solar mass BH would cause the whole back end (if not first the whole front end) of the Sun to explode as about a million years of stored up photons in the Sun's radiative zone now encounter protons that are suddenly in free-fall (if only for a couple of minutes).

<<The radiative zone is just beyond the core of the Sun. It gets its name from its primary method of heat transfer: the radiation of light. As our photon leaves the core and enters the radiative zone, it encounters an obstacle: densely packed protons. They are so crammed together, photons can’t travel more than a few millimeters without hitting another one. Each time one does, it loses some of its energy and is scattered in a random direction. It can take anywhere from a few thousand to a few million years for one photon to escape. It’s not just the light from distant stars that takes millions of years to reach us; the light from our own Sun does too!>>

It's very good for us that we're not irradiated with gamma ray photons from the Sun's core. Indeed, this energy needs to be throttled back greatly or life on Earth wouldn't be possible.

So is something like a Supernova the most likely outcome Art?

That's the way I see it, Bruce.

Solar mass BH's are too small to eat very much but their gravitational fields will reek havoc with a million years of pent up photons.

[Chris Peterson]

Solar mass BH's are too small to eat very much but their gravitational fields will reek havoc with a million years of pent up photons.

By "solar mass BH" I assume you mean "several solar mass BH"? I don't believe there's any known mechanism for producing a one solar mass black hole (outside of some simple speculation).

[BDanielMayfield]

IMO, even a 1 solar mass BH would cause the whole back end (if not first the whole front end) of the Sun to explode as about a million years of stored up photons in the Sun's radiative zone now encounter protons that are suddenly in free-fall (if only for a couple of minutes).

It's very good for us that we're not irradiated with gamma ray photons from the Sun's core. Indeed, this energy needs to be throttled back greatly or life on Earth wouldn't be possible.

So is something like a Supernova the most likely outcome Art?

That's the way I see it, Bruce.

Solar mass BH's are too small to eat very much but their gravitational fields will reek havoc with a million years of pent up photons.

This is fascinating. But why in your opinion should the Sun's radiative zone protons in free-fall be able to suddenly release pent up photons? Wouldn't the photons still have to take their random walk time bouncing through an even denser field of protons?

Bruce

[neufer]

[b][color=#0000FF]Transient Solar Oscillations Driven By [comet sized] Black Holes Ref: arxiv.org/abs/1106.0011:[/color][/b]

---

But why in your opinion should the Sun's radiative zone protons in free-fall be able to suddenly release pent up photons? Wouldn't the photons still have to take their random walk time bouncing through an even denser field of protons?

I envision the exiting BH as stretching the back end of the Sun out like taffy allowing the radiation zone photons engage in a runaway prison break scenario.

I think that is what is probably going on with the original comet sized BH analysis ... on a minuscule scale, of course.

By "solar mass BH" I assume you mean "several solar mass BH"?
I don't believe there's any known mechanism for producing a one solar mass black hole (outside of some simple speculation).

• Whatever!

I find the idea of the Sun being skewered by such a large BH rather fanciful to begin with.

It's just simpler to do my gedanken experiment on a 1 solar mass BH.

[rstevenson]

To add realism, not all of Rob's 'rag tag, refuge fleet' are gonna make it.

My plot outline already has a rather messy ending for one hapless group that left ill-prepared, and a quiet but probably final ending for another. (Or was it final? Maybe a sequel?) But somebody has to survive.

... On the one hand, all this uncertainty allows the author a fair degree of flexibility. On the other, it means there's a good chance that any proposed scenario will be wrong, and possibly demonstrated to be so not long after publication.

That's another of the great traditions of science fiction. It's quite rare that an author manages to predict accurately. Most avoid the issue by engaging in vigorous hand waving to keep the readers' attention transfixed while the details pass by unnoticed.

Once in a while an author comes very close... In his Trouble on Triton, Samuel R. Delany describes something very like tablet computers accessing a universally available database. A detail that might still be prescient is that a great deal of personal information is also easily accessible.

Rob

[Chris Peterson]

I find the idea of the Sun being skewered by such a large BH rather fanciful to begin with.

Indeed. In fact, I'd suggest it offers the writer an opportunity to consider the collision a deliberate act.

[Doum]

Rob, here some information that might be helpfull to mention for those long space years travel of your spaceship. Just a tought.

http://www.spacedaily.com/reports/UNSW_ ... g_999.html

UNSW researchers have made a discovery that could lead to a revolutionary drug that actually reverses ageing, improves DNA repair and could even help NASA get its astronauts to Mars.

Also, people may not panic???

http://www.terradaily.com/reports/Video ... s_999.html

Many assume the world will end in chaos, a complete breakdown of the social order. The results of a new video game study suggest otherwise.

Mehh, what will it be?

[rstevenson]

Thanks Doum. Interesting stuff.

Rob

[BDanielMayfield]

It was an interesting diversion to consider the Sun vs. BH case. It has demonstrated how counter-intuitively hard it is to feed a black hole. They seem to be better at ripping things apart and dispersing them than actually scarfing them down.

Bruce

[Chris Peterson]

It was an interesting diversion to consider the Sun vs. BH case. It has demonstrated how counter-intuitively hard it is to feed a black hole. They seem to be better at ripping things apart and dispersing them than actually scarfing them down.

The important thing to remember about stellar mass black holes is that they are, in almost all dynamical respects, no different from stars. Black holes are no more attractive to outside material than stars. Things only get different when you are very close to the black hole- well inside a typical stellar radius. Because a black hole is so small, it can get closer to something than a star without actually colliding. But in reality, things seldom get that close in any case.

[BDanielMayfield]

It was an interesting diversion to consider the Sun vs. BH case. It has demonstrated how counter-intuitively hard it is to feed a black hole. They seem to be better at ripping things apart and dispersing them than actually scarfing them down.

The important thing to remember about stellar mass black holes is that they are, in almost all dynamical respects, no different from stars. Black holes are no more attractive to outside material than stars. Things only get different when you are very close to the black hole- well inside a typical stellar radius. Because a black hole is so small, it can get closer to something than a star without actually colliding. But in reality, things seldom get that close in any case.

Yes. Take, for example, our 5 solar massed BH compared to a main sequence star of the same mass. A spacecraft should be able to safely approach much closer to the BH than it could to the star.

We've discussed possible outcomes for the Sun at length. Let's consider what might happen to the Sun's family of planets in Ron's scenario. Would any of them remain in solar orbit (If the Sun somehow doesn't detonate as Art expects)? Might some or even all of the planets be captured into orbiting the BH?

Bruce

[rstevenson]

We've discussed possible outcomes for the Sun at length. Let's consider what might happen to the Sun's family of planets in Rob's scenario. Would any of them remain in solar orbit... ?

As the BH approaches, the planets will be dragged 'up' in their orbits. They'll be pulled back down later as the BH leaves the Solar System. Such oscillations would eventually dampen down -- if that's all that happened. However, that's only the simplest effect and the least problematic.

During the time that the BH is somewhere close to the Sun there will be six solar masses pulling on the planets, not the usual one solar mass. That will cause the planets to spiral inward towards the Sun, which will not be a particularly good thing for us fragile humans. I've yet to work out how much the Earth's orbit will change -- it's going to require a little borrowed time on a super computer -- but I expect the Solar System will look nothing like what it does now after the BH passes through.

Might some or even all of the planets be captured into orbiting the BH?

Conceivably, something that is quite close will get pulled along -- maybe Mercury, maybe just some of the objects the BH passes on its way through the assumed Oort Cloud. I expect the planets will remain in what would still be technically orbits around Sol, though the kinds of orbits will be quite varied. How about Venus being flung into a 4000-year ellipse, to take just one possible outcome. The big guys, Jupiter and Saturn, will be least affected I think, as would the distant planets Uranus and Neptune. But least affected is still not unaffected. It ain't going to be pretty.

Rob

[Doum]

As the BH approaches, the planets will be dragged 'up' in their orbits. They'll be pulled back down later as the BH leaves the Solar System. Such oscillations would eventually dampen down -- if that's all that happened. However, that's only the simplest effect and the least problematic.

Rob

Yes, at first the planet will be dragged up but when the black hole is in center of the sun and start leaving it, the planet will already be closer to the sun and the black hole. So i think the planet will be pull back down but more down because gravity will be stronger. They will be pull down under their initial orbit they have. They will orbit the sun with a new angle to the sun. Quite a mess.

[BDanielMayfield]

As the BH approaches, the planets will be dragged 'up' in their orbits. They'll be pulled back down later as the BH leaves the Solar System. Such oscillations would eventually dampen down -- if that's all that happened. However, that's only the simplest effect and the least problematic.

Rob

Yes, at first the planet will be dragged up but when the black hole is in center of the sun and start leaving it, the planet will already be closer to the sun and the black hole. So i think the planet will be pull back down but more down because gravity will be stronger. They will be pull down under their initial orbit they have. They will orbit the sun with a new angle to the sun. Quite a mess.

Rob, sorry for the name misspelling. I don't think that there would be any oscillations about the planes of planetary orbits since the "gravity well" curvature of spacetime caused by the BH wouldn't have ripples.^{clarification needed?} I also don't think you would need a super computer to model this. All you may need is solar system simulator software that allows for the introduction of an extra body. Dance of the Planets might be able to do this.

Doum, orbits would be even wilder than what you suggest, imo. I think capture by the BH is most likely, since its mass is so much greater than the Sun. It's 5:1 on the way in but maybe 6:1 (or greatly more if Art is right) on the way out. "Quite a mess" for sure.

Bruce

[Chris Peterson]

As the BH approaches, the planets will be dragged 'up' in their orbits. They'll be pulled back down later as the BH leaves the Solar System. Such oscillations would eventually dampen down -- if that's all that happened.

Planets can't oscillate up and down in their orbits. They simply orbit on a plane centered on the system's center of mass- normally the Sun, but for a period of some years before and after the collision a moving point between the Sun and the black hole.

During the time that the BH is somewhere close to the Sun there will be six solar masses pulling on the planets, not the usual one solar mass. That will cause the planets to spiral inward towards the Sun, which will not be a particularly good thing for us fragile humans. I've yet to work out how much the Earth's orbit will change -- it's going to require a little borrowed time on a super computer -- but I expect the Solar System will look nothing like what it does now after the BH passes through.

Indeed, the system will be massively disrupted. No need for a supercomputer, however. Your phone could handle the simulation.

Conceivably, something that is quite close will get pulled along -- maybe Mercury, maybe just some of the objects the BH passes on its way through the assumed Oort Cloud. I expect the planets will remain in what would still be technically orbits around Sol, though the kinds of orbits will be quite varied. How about Venus being flung into a 4000-year ellipse, to take just one possible outcome. The big guys, Jupiter and Saturn, will be least affected I think, as would the distant planets Uranus and Neptune. But least affected is still not unaffected. It ain't going to be pretty.

I think it's as likely that most or all of the planets would be ejected from the system as rogues as that they would remain in closed solar orbits.

[BDanielMayfield]

From much earlier, there was this exchange:

If the black hole conveniently passes through the Sun from pole to pole, there should be no terrible consequences for our system of planets. Everything should just keep rolling around where it's supposed to roll.

Ever play around with a gravity simulator program? Throw another stellar mass in our system, even passing through from north to south, and it's game over for planetary orbits. Everything will be rolling in a new place. Not good.

Does anyone reading this have such a "gravity simulator program"? It would be nice to get a report of what such a program would show with this scenario.

Bruce

[BDanielMayfield]

Might some or even all of the planets be captured into orbiting the BH?

Conceivably, something that is quite close will get pulled along -- maybe Mercury, maybe just some of the objects the BH passes on its way through the assumed Oort Cloud. I expect the planets will remain in what would still be technically orbits around Sol, though the kinds of orbits will be quite varied. How about Venus being flung into a 4000-year ellipse, to take just one possible outcome. The big guys, Jupiter and Saturn, will be least affected I think, as would the distant planets Uranus and Neptune. But least affected is still not unaffected. It ain't going to be pretty.

Rob

Remember the old, what falls faster in a vacuum, a feather or a cannonball experiment? Distance from the BH is the controlling factor, not the planet's mass. Therefore, ignoring the small pulls of the planets on each other, each planet is effected solely by its instantaneous momentum and the attractions of the two big bodies in the system, the Sun and the BH. Therefore the orbits of the planets will be affected in decreasing amounts with their original distances from the Sun.

Bruce

[Chris Peterson]

Might some or even all of the planets be captured into orbiting the BH?

Conceivably, something that is quite close will get pulled along -- maybe Mercury, maybe just some of the objects the BH passes on its way through the assumed Oort Cloud. I expect the planets will remain in what would still be technically orbits around Sol, though the kinds of orbits will be quite varied. How about Venus being flung into a 4000-year ellipse, to take just one possible outcome. The big guys, Jupiter and Saturn, will be least affected I think, as would the distant planets Uranus and Neptune. But least affected is still not unaffected. It ain't going to be pretty.

Remember the old, what falls faster in a vacuum, a feather or a cannonball experiment? Distance from the BH is the controlling factor, not the planet's mass. Therefore, ignoring the small pulls of the planets on each other, each planet is effected solely by its instantaneous momentum and the attractions of the two big bodies in the system, the Sun and the BH. Therefore the orbits of the planets will be affected in decreasing amounts with their original distances from the Sun.

FWIW, playing with a very simple simulator I note that simply doubling the mass of the Sun for a couple of months and then taking it back to normal is sufficient to eject the Earth from the Solar System.

[rstevenson]

FWIW, playing with a very simple simulator I note that simply doubling the mass of the Sun for a couple of months and then taking it back to normal is sufficient to eject the Earth from the Solar System.

Well that should simplify my plot.

Rob

[BDanielMayfield]

Therefore the orbits of the planets will be affected in decreasing amounts with their original distances from the Sun.

I need to correct this point. I was wondering where the points would be where the gravitational forces pulling on each planet by the Sun and the BH would be equal. A little math shows that this is reached at the points where the BH is the square root of 5 (~2.236) times the planet-sun distance. This is way out at 67.3 AU for Neptune down to 0.865 AU for Mercury. Therefore the BH would mess with the outer planets over a much longer duration than the inner planets.

Bruce

[BDanielMayfield]

The square root of five is an interesting number when it is the hypotenuse of a right triangle.

a^2 + b^2 = h^2

If a is the Sun-Planet distance (say, 1 AU in Earth's case) then 1² + b^² = 5 and b, the Sun-BH distance = 2

Therefore on average, each planet would feel the same pull from the Sun and the BH when the Sun-BH distance is twice the Sun-Planet distance. So for Neptune the BH attraction becomes greater than the Sun's when the BH is approximately 60 AU from the Sun.

Bruce