9 y.o. question: will a spoon of neutron star matter explode?

[yapi]

TL;DR

Got a question from my 9.y.o. son: what will happen if a famous Everest heavy spoon of neutron star matter is actually removed from the star?

Greetings All,

Well, this is the question from my 9 y.o. son: what will happen if a famous Everest heavy spoon of neutron star matter is actually removed from the star? I am inclining to his version that it will explode rather quickly, e.g. neutrons will quickly decay into protons-electrons pairs and stuff expand rapidly releasing a lot of energy that used to bind protons and electrons into neutrons.

Is there some consensus regarding the outcome of such dodgy experiment?

 

[etotheipi]

releasing a lot of energy that used to bind protons and electrons into neutrons.

What does this mean?

 

[yapi]

What does this mean?

We, myself with my 9 y.o., were guessing that as neutron is unstable when not inside of an atom, then when it decays it will produce proton + electron and some extra stuff (energy, neutrino?) and that all this put together will look to the external observer exactly like the spoon of starry stuff just exploded. Hence the question. Maybe there is a plausible answer.

 

[Drakkith]

It will either explode, or, somewhat less rapidly, 'boil away' as neutrons turn into electrons and protons and the released energy is turned into heat. Considering that a block of plutonium-238 Oxide, with a half life for the plutonium of 87.7 years, generates enough self heat to turn cherry red, neutronium would generate far more heat given its much shorter half-life of about 15 minutes. Enough to vaporize itself in short order without the immense gravity of the rest of the neutron star holding it down.

But it probably just explodes as there is nothing to hold the neutrons together anymore.

 

[jbriggs444]

It will either explode, or, somewhat less rapidly, 'boil away' as neutrons turn into electrons and protons and the released energy is turned into heat. Considering that a block of plutonium-238 Oxide, with a half life for the plutonium of 87.7 years, generates enough self heat to turn cherry red, neutronium would generate far more heat given its much shorter half-life of about 15 minutes. Enough to vaporize itself in short order without the immense gravity of the rest of the neutron star holding it down.

But it probably just explodes as there is nothing to hold the neutrons together anymore.

Suppose that we use a rigid and well-insulated spoon which we open up in our lab. Then we can further nail down that "probably" by asking:

What is the temperature of the neutronium at the surface of this neutron star?

What is the bulk modulus of neutronium under the atmospheric pressure at the surface of this neutron star?

What is the atmospheric pressure at the neutronium surface of this neutron star?

Google can come up with some of these answers.

The properties of this carbon atmosphere are remarkable. It is only about four inches thick, has a density similar to diamond and a pressure more than ten times that found at the center of the Earth. As with the Earth's atmosphere, the extent of an atmosphere on a neutron star is proportional to the atmospheric temperature and inversely proportional to the surface gravity. The temperature is estimated to be almost two million degrees, much hotter than the Earth's atmosphere. However, the surface gravity on Cas A is 100 billion times stronger than on Earth, resulting in an incredibly thin atmosphere.

I don't guess we need to worry much about the bulk modulus. Two million degrees is going to mean an explosion will ensue.

 

[yapi]

To respect the scientific tradition of a spherical cow in a vacuum, let's assume that we have a spoonful volume of neutronium in a vacuum of space far enough from any relevant scale strong gravity, e.g. (I am conjecturing here): let's imagine crazy fast traveling (ejected by supermassive black holes) pair of neutron stars that had direct head-to-head collision with each other and their combined mass and kinetic energy just not enough to form yet another black hole. Surely there bound to be some pieces of neutronium flying in all directions.

One of this pieces - our Everest heavy, two million degrees hot with 10.2 mins half-life spoon of the starry stuff.

So my understanding is that the total energy of two million degrees will instantly evaporate this spoon of neutronium into a cloud of crazy fast neutrons, which will decay into the protons, electrons and other stuff like a lot of gamma rays.

It will instantly explode then.

This renders the second question of my 9 y.o. as inapplicable: will the spoonful of neutronium go right through the Earth to it's center or will it stop at some stage. Two million degrees of the 7.5E+14 Kg of neutronium will probably be enough to simply destroy the Earth ( 5.972E+24 kg) but there is no way that such a spoon can ever reach the Earth.

 

[Vanadium 50]

Think of this spoonful of material as a spring. On the star's surface it's under 10¹⁸ tons of compression. When this is released, there will be a release of all this pressure. Kaboom.

 

[jbriggs444]

Think of this spoonful of material as a spring. On the star's surface it's under 10¹⁸ tons of compression. When this is released, there will be a release of all this pressure. Kaboom.

That is why I was after the bulk modulus earlier. The quantity of energy released depends (to first order anyway) on the product of bulk modulus and pressure.

 

[Vanadium 50]

It doesn't matter what the exact number is. It's still kaboom.

 

[yapi]

Thanks a lot.

My 9 y.o. will be delighted to know that his intuitively conjectured kaboom has scientific merits to it. The spring analogy will be particularly helpful.