Learning Physics: How Do Neutron Stars Form?

In summary, neutron stars form when a star runs out of fuel and its gravity overcomes the degeneracy pressure of its collapsing neutrons. The outward pressure that prevents the star from collapsing further is neutron degeneracy pressure. This is not affected by temperature, so even if the star's heat from fusion runs out, it will not collapse unless it is influenced by accretion from another object.
  • #1
madphysics
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Hi guys, I'm not to great at physics and all but I want to learn more. I hope you guys can help me in that aspect.First of all, how do neutron stars form? I was told their electrons shrink into their nucleuses and therefore the whole star shrinks, but what causes the atoms to behave like that?
 
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  • #2
Gravity.

Stars are balanced between gravity trying to squeeze everything together and some outward pressure trying to push it apart.
When a star runs out of fuel, ie. ends up being made of stuff that dones't give off enough energy in a fussion, there is no outward radiation pressure to push the stuff apart.
In neutron stars the pressure to keep them up comes from degeneracy pressure - basically the neutrons can't be pressed together any tighter.
If the star's gravity is big enough to overcome this it becomes a black hole.
 
  • #3
What is the outward pressure? It's not inertia like planets. Is it the process of fusion?
 
  • #4
You got it - heat from fusion keeps the star from imploding...until the fuel runs out.
 
  • #6
madphysics said:
What is the outward pressure? It's not inertia like planets. Is it the process of fusion?

The outward "pressure" is the Pauli principle
 
  • #7
The outward pressure is neutron degeneracy pressure. Electron degeneracy pressure is what stops white dwarfs collapsing in but when this is less than the gravitational pressure, inverse beta decay creates neutrons. Neutron stars generally have a radius of (electron mass/proton mass)*white dwarf radius which turns out to be tiny, something like 10km!

Collapse is nothing to do with heat from fusion. Even if the heat from a stable neutron star had run out and it reached a few K, it would not collapse because the degeneracy pressure is not a function of temperature. The only way to make a stable neutron star tip over the edge to a black hole is by accretion from another object like a second star in a binary system.
 
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1. What is a neutron star?

A neutron star is a highly dense and compact remnant of a supernova explosion. It is composed almost entirely of neutrons and has a mass greater than the sun, but with a much smaller diameter of only about 10-15 kilometers. Neutron stars have extremely strong magnetic fields and rotate at incredibly high speeds, making them one of the most fascinating objects in the universe.

2. How do neutron stars form?

Neutron stars are formed when a massive star runs out of nuclear fuel and undergoes a supernova explosion. During this process, the outer layers of the star are blown away, leaving behind a dense core of mostly neutrons. This core collapses under its own gravity, resulting in a neutron star.

3. What role does gravity play in the formation of neutron stars?

Gravity is the driving force behind the formation of neutron stars. As the massive star's core collapses, the gravitational force becomes stronger and stronger, causing the core to become more and more compact. This results in a neutron star with an extremely high density and strong gravitational pull.

4. How are neutron stars different from other types of stars?

Neutron stars are different from other types of stars in several ways. They are much smaller and denser than regular stars, and they also have much stronger magnetic fields. Neutron stars also have a unique surface composition, with a thin crust of solid nuclear matter and a core made up of superfluid neutrons.

5. What can we learn from studying neutron stars?

Studying neutron stars can provide us with valuable insights into the fundamental laws of physics. They can also help us understand the life cycle of stars and the processes that occur during a supernova explosion. Additionally, the extreme conditions on neutron stars can help us test and refine our understanding of gravity and nuclear physics.

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