# Does the plasma at the center of a star act like a solid?

• B
• ktoz
In summary, the conversation discusses the properties of the plasma at the center of stars and how extreme pressure and temperature can affect its behavior. The participants also question whether the plasma could potentially behave like a solid due to the constraints on particle movement.
ktoz
I was passing time by Googling the properties of the sun (temperature, mass, etc) and got to wondering what lies at the center of stars. I found out its plasma under roughly 340 billion atmospheres of pressure.

I realize Boyles law may not be strictly meant for plasmas, but using it I calculated the volume change of 1 cubic foot of air at 340 billion atmospheres to roughly the volume of 93 hydrogen atoms.

Since there are roughly 1.52*10^24 atoms in one square foot of air at standard pressure, that many atoms squeezed to such a small volume, would seem to suggest that the plasma would act like a very rigid, very hard solid. Is that the case?

Have you taken the temperature of the plasma into account?

Drakkith said:
Have you taken the temperature of the plasma into account?
I did and I'm not sure exactly how that would counteract the enormous pressure. Isn't temperature just the average number of collisions in an area per unit time?

If you could sum the speeds of every individual particle in a given volume before and after the decrease, the values would be the same would they not? Or another way, the collisions per unit area increases, but the actual energy of the collection remains constant. The particles aren't moving any faster, they are just experiencing more collisions per unit time.

At the extreme pressures inside a star, the drastic decrease in volume greatly constrains the degrees of freedom of individual particles. The volume is reduced by so much that distances the individual protons and electrons can travel without collisions are reduced to less than the diameter of a hydrogen atom.

The repulsive forces between electrons and protons would further constrain their motion creating something that behaves like an extremely hard, dense crystal. It would still technically be a plasma, because the electrons are not bound to any protons, but functionally, wouldn't it be a solid?

ktoz said:
I did and I'm not sure exactly how that would counteract the enormous pressure. Isn't temperature just the average number of collisions in an area per unit time?

If you could sum the speeds of every individual particle in a given volume before and after the decrease, the values would be the same would they not? Or another way, the collisions per unit area increases, but the actual energy of the collection remains constant. The particles aren't moving any faster, they are just experiencing more collisions per unit time.
The speeds would increase. Temperature is the average amount of kinetic energy of its constituent particles. Pressure is roughly the number of collisions in an area however which is related to temperature through the Ideal Gas Law.

I understand your reasoning, but perhaps you'd like to define a solid? What about high pressure/atoms being close together gives it properties of a solid?

(Bonus inquiry I had that was similar. The freezing point of water is inversely proportional to the pressure for large pressures. At what temperature does water freeze in an infinitely pressurized location? That is, at what temperature would water become ice if it were at the center of the Sun?)

ktoz said:
I did and I'm not sure exactly how that would counteract the enormous pressure. Isn't temperature just the average number of collisions in an area per unit time?

It is not, though the number of collisions is related to the temperature.

Temperature in an "ideal" gas is given here: https://en.wikipedia.org/wiki/Kinetic_theory_of_gases#Temperature_and_kinetic_energy
Basically: "the average molecular kinetic energy is proportional to the ideal gas law's absolute temperature".

ktoz said:
If you could sum the speeds of every individual particle in a given volume before and after the decrease, the values would be the same would they not? Or another way, the collisions per unit area increases, but the actual energy of the collection remains constant. The particles aren't moving any faster, they are just experiencing more collisions per unit time.

The particles are indeed moving much faster in the core at the huge temperatures therein.

ktoz said:
The repulsive forces between electrons and protons would further constrain their motion creating something that behaves like an extremely hard, dense crystal. It would still technically be a plasma, because the electrons are not bound to any protons, but functionally, wouldn't it be a solid?

Not as far as I know. I've never heard the Sun's core described as such.

## 1. How does the plasma at the center of a star behave?

The plasma at the center of a star behaves differently than a solid. It is highly ionized and has a high energy state, allowing it to flow and move freely like a gas rather than being rigid like a solid.

## 2. Can the plasma at the center of a star support weight and pressure like a solid?

No, the plasma at the center of a star cannot support weight and pressure like a solid. It is not a solid structure and does not have the same properties to withstand external forces.

## 3. Is the plasma at the center of a star stable?

The plasma at the center of a star is constantly undergoing fusion reactions, which create a balance between the inward force of gravity and the outward force of radiation. This balance helps to stabilize the plasma, but it is not completely stable as it is constantly changing and evolving.

## 4. How does the plasma at the center of a star contribute to its energy production?

The plasma at the center of a star is where nuclear fusion reactions occur, releasing a tremendous amount of energy. These reactions fuse hydrogen atoms into helium, releasing energy in the form of light and heat.

## 5. Can the plasma at the center of a star solidify?

No, the plasma at the center of a star cannot solidify. The extreme temperatures and pressures at the core of a star prevent the plasma from becoming a solid. It would require a significant decrease in temperature and pressure, which is not possible in the intense conditions of a star's core.

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