What would happen to a thimble full of a neutron star if you brought it to Earth?

13 December 2016

Neutron_star_illustrated.jpg

Artist's illustration of an 'isolated neutron star' -- one without associated supernova remnants, binary companions or radio pulsations.

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Question

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.

Answer

Physicist Andrew Pontzen pontificated about Jane's question...

Andrew - Well, it's not advisable to bring a thimble full of neutron star here. Neutron stars are a gift really, they are just the weirdest things out there in space, or amongst the weirdest things.

Something like two times the mass of our own Sun and yet it's concentrated into a tiny, tiny region about twenty kilometres across and, for comparison, the size of the Sun itself is more like a million kilometers across. So you're cramming a huge amount of stuff into a tiny amount of space almost getting towards black hole type proportions.

Chris - And why are they called neutron stars?

Andrew - They're called neutron stars because when you do that, the thing that actually happens is that you cram all of the electrons, which are the negatively charged particles, into the protons. And that actually turns them into neutrons because you combine negatively and positively charged particles and you end up with only neutrons left over.

That, in fact, is part of the reason why you would never want to take a thimble full of this material here to Earth, a number of things would happen. First of all to get that much stuff in that small a space you need to compress it down and that's held together by the immense gravity on a neutron star. But if you take just a thimble full of it, that gravity's gone and, essentially, this thing is just going to spring apart really fast. And you're talking about a Mount Everest or perhaps several Mount Everest's worth.

Chris - From one thimble full?

Andrew - From one thimble full which is why we always talk about the thimble fulls of course because it's a great statistic, an entire Mount Everest packed into a thimble. But it's going to try and spring apart to be the size of Mount Everest, so that's not great to start with.

But, even worse than that, even if you survived that happening, then you have all of these neutrons, and neutrons on their own are not actually stable particles. They're going to try and decay back down to the protons and electrons, which most of them were formed from in the first place and that process of nuclear decay is not pretty either. It's going to release a huge amount of energy. I tried doing a bit of an estimate of this, it does depend a bit on the exact assumptions you make, but I think it's something like one trillion H bomb explosions. That much energy is going to be released over the space of a few minutes as all of these neutrons turn back into protons and electrons.

Chris - That could give even a photon torpedo a run for it's money, couldn't it, in Start Trek?

Andrew - It certainly could. And, if you bear in mind that's a sort of factor of ten, no even bigger than that, it's probably a factor of ten thousand times more energy than was involved in the collision with the asteroid that we think killed the dinosaurs, you get the sense of just the enormous amounts of energy that would be released by doing this. So, please, please, please, don't do it!

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