When a protostar stops contraction

[shirin]

It is written that when the gas of the protostar is completely ionized, it stops contraction and it gets into hydrostatic equilibrium. I don't understand why?

 

[ibysaiyan]

It doesn't as far as my knowledge on stellar evolution goes.When the star reaches "main sequence" stage and produces enough outward radiation pressure through nuclear fusion to counter inward pull of gravity,it's at this stage when hydrostatic equilibrium is achieved.
P.S: does it mention that the star is shrinking ? or just attains equilibrium ? I think ions as the no. of ions increases they tend to absorb heat than radiating away.That might be the reason?

-ibysaiyan

 

[qraal]

It is written that when the gas of the protostar is completely ionized, it stops contraction and it gets into hydrostatic equilibrium. I don't understand why?

Ionization means the object is no longer transparent to heat/light and so the rate of contraction slows down to match the loss of heat via radiation from the object's photosphere. It can only contract if it can lose heat, else it remains inflated. Fusion energy provides a source of internal heat, keeping stars puffed up else they'd contract to white dwarf size via gravitational collapse because their cores are degenerate matter.

 

[shirin]

why the ionization means the object is no longer transparent to heat/light? I can understand it for nuclea but what about free electrons? what has happened to them by now? because they can tranfer heat/light!

 

[pmacias]

I can explain the process of a protostar stopping contraction and entering hydrostatic equilibrium. When a protostar is formed, it is made up of gas and dust particles that are attracted to each other by gravity. As these particles come closer together, they increase in temperature and pressure, causing the protostar to contract.

However, as the protostar continues to contract, the gas particles become more and more tightly packed, resulting in collisions between them. These collisions cause the gas particles to gain energy and become ionized, meaning that they lose electrons and become positively charged ions.

As more and more gas particles become ionized, the protostar's gas becomes highly conductive, meaning that it can efficiently transfer heat and energy. This allows the protostar to reach a state of hydrostatic equilibrium, where the inward gravitational force is balanced by the outward pressure of the gas.

In simpler terms, the gas particles in the protostar are able to push back against the force of gravity, preventing further contraction. This is due to the high temperature and ionization of the gas, which allows it to exert a strong outward pressure.

In conclusion, the protostar stops contracting and enters hydrostatic equilibrium when the gas becomes completely ionized because the ionized gas is able to resist the force of gravity and maintain a stable size and shape.