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Author Topic: What would happen to a thimble full of a neutron star if you brought it to Earth?  (Read 385 times)

Offline thedoc

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Jane Maddin  asked the Naked Scientists:
   Hi Chris, et al.
I have a question related to Neutron Stars.

When scientists talk about Neutron Stars they talk about how much a thimble full of the material that makes up a Neutron Star would weigh if you had one here on the surface of the Earth.

What I would like to know is what would ACTUALLY happen if you had a thimble's worth of Neutron Star material here. Once it is removed from the gravity of the rest of the star, would a thimble's worth piece of neutron star remain in that state? Would it expand to the size of the mountain? (sort of like compressed gas would expand if it was removed from the container that was providing the compression)

I hope my question is clear. I guess I am asking if it is the gravity of the surrounding body that would maintain the 'pressure' that forces all the atomic particles so tightly together, or whether this would be self sustaining.

Thanks! I'm looking forward to the answer to this.
Jane Maddin
Salmon River, Nova Scotia, Canada

--
"No distance of place or lapse of time can lessen the friendship of those who are thoroughly persuaded of each other's worth."  ~Robert Southey

   
What do you think?
« Last Edit: 05/10/2016 09:53:02 by _system »


 

Online evan_au

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Quote from: Jane Maddin
What I would like to know is what would ACTUALLY happen if you had a thimble's worth of Neutron Star material here.
Leaving aside the minor difficulties of mining a thimble of neutron star stuff, lifting it off the star against enormous gravity and safely transporting it to a soft landing on Earth....

It would have (at a quick guess):
- A temperature of perhaps a million degrees, so it would be glowing in X-Rays
- If it carried any magnetic field from the neutron star, would cause any magnetic materials to be distorted
- A pressure about 1030 higher than atmospheric pressure, so it would immediately explode, with high-energy neutrons traveling at close to the speed of light
- These neutrons would make any elements they struck radioactive, and kill any living thing within range
- The density is so high that any remaining compressed material would free-fall towards the center of the Earth
- Over the next 12 minutes about half of the neutrons would decay into protons, electrons and neutrinos, and another quarter in the next 12 minutes, etc

So it would leave a very big crater, blast some of Earth's atmosphere into space, and leave a lot of radioactive debris.

Good luck getting your thimble back at the end of the experiment!

See: https://en.wikipedia.org/wiki/Neutron_star#Properties
 
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Offline Semaphore

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The explosive blast would be massive. Is there any way to calculate the force, say in terms of Hiroshima-grade bombs? My guess (unsupported by facts) would be that it might destroy all life on Earth.
 

Online jeffreyH

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Well you have no protons to begin with so as the material is moved to higher gravitational potential you will start to get neutron decay which would then enable the formation of alpha particles (helium nuclei). This would tend to disrupt the integrity of the matter in the immediate vicinity. This would likely involve a very loud bang. Except it would be inaudible in vacuum.
 

Online evan_au

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Quote from: jeffreyH
you will start to get neutron decay which would then enable the formation of alpha particles (helium nuclei)
I was wondering about that...
- An isolated neutron has a half life of around 12-15 minutes
- But what about a concentrated mass of neutrons?

The surface of a neutron stars is not pure neutrons - it is thought that there should be a thin atmosphere of iron nuclei and other "normal" matter  on the surface. 

But a thimble full of neutronium would contain around 1036 neutrons.
- If we could create a nucleus with that ratio of protons to neutrons, the nucleus would be very unstable
- The Pauli exclusion principle would put a lot of the neutrons into pretty high energy levels.
- If some of those neutrons turned into protons, they would have much lower energy levels, so the decay is more energetically favorable than for an isolated neutron
- Against this, neutron decay into proton+electron+neutrino involves the weak nuclear force, which is relatively slow.

If the whole mass of neutronium rapidly turned into alpha particles (in nanoseconds, for example), that would produce a massive explosion!

Can anyone suggest which effects would dominate?
 

Online jeffreyH

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I would imagine that the important point to consider would be the velocity away from the neutronium source and the resulting change in gravitational potential. This would have the greatest impact on the rate of neutron decay.
 

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