Star Trek (2009) and black hole planet collapse

[sshai45]

Hi.

I was wondering about this. In the "Star Trek" movie of 2009, the destruction of the planet Vulcan is shown, by a black hole being formed in its core. I'm curious: supposing you had some means to create, or collapse part of the planet to form, a black hole in its core, what would, according to real physics, the ensuing destruction of the planet look like, versus how it was depicted in this film?

 

[Simon Bridge]

You somehow produce a stable quantum black hole inside a planet?
Phil Plait already got that covered:
http://blogs.discovermagazine.com/badastronomy/2009/05/08/ba-review-star-trek/#.UsEDdnntkjA

 

[phyzguy]

Hi.

I was wondering about this. In the "Star Trek" movie of 2009, the destruction of the planet Vulcan is shown, by a black hole being formed in its core. I'm curious: supposing you had some means to create, or collapse part of the planet to form, a black hole in its core, what would, according to real physics, the ensuing destruction of the planet look like, versus how it was depicted in this film?

I think the whole thing would happen much, much faster than what is depicted in the movie. I have seen simulations of a neutron star collapsing into a black hole, and the time scale is milliseconds. Also, because the planet is rotating, it could not just fall in and disappear as shown in the movie, because it couldn't shed its angular momentum fast enough. So I think part of the planet would be ejected into space, and part would form an accretion disk around the black hole.

 

[Simon Bridge]

But in the neutron-star example, the mass to form the black hole comes from the star.
In the movie - the mass comes from the planet ... and whatever effect the physics of red unobtainuim has.
How it would go depends on what you assume that physics is.

See the link in post #2.

 

[phinds]

Since the whole thing is magic rather than science, you can pretty much make up whatever rules you like.

 

[sshai45]

Since the whole thing is magic rather than science, you can pretty much make up whatever rules you like.

Well, in my case I was imagining that maybe the creation of the black hole may be "magic" as you say, but once created, it acts like a real black hole. What happens?

 

[sshai45]

I think the whole thing would happen much, much faster than what is depicted in the movie. I have seen simulations of a neutron star collapsing into a black hole, and the time scale is milliseconds. Also, because the planet is rotating, it could not just fall in and disappear as shown in the movie, because it couldn't shed its angular momentum fast enough. So I think part of the planet would be ejected into space, and part would form an accretion disk around the black hole.

So if "part is ejected", then might it look more like Alderaan blowing up in Star Wars?

 

[DHF]

Once the apropriate amount of pixie dust ... I mean "Red Matter" is added to form said black hole, the planet would shred rather then explode. It is being sucked in on itself as its spinning so the entire planet would turn to mulch and some of it would spiral into the hole and part of it would spin outwards. Google video simulations of Black holes feeding to see graphics on what it looks like.

 

[sshai45]

Once the apropriate amount of pixie dust ... I mean "Red Matter" is added to form said black hole, the planet would shred rather then explode. It is being sucked in on itself as its spinning so the entire planet would turn to mulch and some of it would spiral into the hole and part of it would spin outwards. Google video simulations of Black holes feeding to see graphics on what it looks like.

Won't the matter at some point reach several million degrees somewhere in the process? What kind of radiation would that throw off (the "4th power law" and Planck (for the peak wavelength) suggest "oh crap", but that doesn't take into account the fact that a disrupted, swirling mass of planetary stuff is not the same as a simple, ideal blackbody radiator, for one, there could be a lot of intervening material between the hot core and the outside)? How much trouble would the Enterprise have been in, with all that going on just a few tends of thousands of km away from it?

 

[DHF]

oh If you introduce even a shred of reality into this scenario then the Enterprise is dust. The radiation alone probably would have killed them all.

 

[HomogenousCow]

In order to generate that much "suction" through gravitational means, that stuff inside the planet must have orders upon orders and orders and then some more orders of mass relative to the planet.

 

[phinds]

In order to generate that much "suction" through gravitational means, that stuff inside the planet must have orders upon orders and orders and then some more orders of mass relative to the planet.

What? You don't believe in the magic of "red matter" ?

 

[Algr]

Also, because the planet is rotating, it could not just fall in and disappear as shown in the movie, because it couldn't shed its angular momentum fast enough.

If the black hole forms in the center of the planet, then most of the insides of the planet are gone by the time you see the surface collapse. The gravity at the surface would not change, but the mater holding it up would vanish, causing everything to fall inward, even at the equator where angular momentum is greatest. If anything got ejected, I can't see it escaping past where the original surface had been before falling back in.

Phil Platt says that the black hole (I assume he means the event horizon) would only be the size of a golf ball, but it is still consuming matter from all directions at the speed of light! And given the intense pressure inside a planet, I think there would be a much larger "heavy enough" horizon where the inward flow pressure would prevent anything BUT light from escaping. Maybe even a "neutron horizon" where everything becomes neutronium before falling into the hole?

There would be plenty of heat generated, but at the core of a planet it is already very hot - would more heat make a difference? And wouldn't the black hole consume much of the extra heat? Until the crust collapses, the heat can't go anywhere else.

(Side note, if two black holes have the same mass, can one be hotter than the other?)

 

[mfb]

If anything got ejected, I can't see it escaping past where the original surface had been before falling back in.

Jets, light, ...?

And given the intense pressure inside a planet

Completely negligible compared to all parameters relevant for the black hole.

Maybe even a "neutron horizon" where everything becomes neutronium before falling into the hole?

Is that a wild speculation or do you have any argument for that?

There would be plenty of heat generated, but at the core of a planet it is already very hot - would more heat make a difference?

The current temperature is completely negligible to typical temperatures of the inner parts of accretion disks.

And wouldn't the black hole consume much of the extra heat?

Not in a way that it would cool down.

(Side note, if two black holes have the same mass, can one be hotter than the other?)

No, but the temperatures outside can vary.

 

[DHF]

Really the whole drama of drilling a hole to the planet's core and dropping a black hole inside served no purpose other then giving the heroes a chance to fight. the show would have been much much shorter if they just pulled up to a planet and shot a pellet of Red matter at it. I think the planet would suffer an equally unpleasant fate. I can't imagine a black hole forming on the surface would be any less destructive then forming at the center.

 

[Simon Bridge]

Wasn't part of the plot that shooting a pellet of red-matter at a star had a devastating effect?
But - villains tend to go for melodrama so maybe the slow inward collapse was a carefully calculated effect: the better to make Spok suffer in a particularly poetic way?

Star Trek is generally pretty silly.