Does Star Evolution Always Lead to Expansion?

In summary, the evolution of a star's core can lead to different outcomes such as expansion, collapse into a white dwarf or neutron star, or collapse into a black hole. Gravity and energy from core fusion play a role in determining the fate of the star. One specific case that can cause expansion is the fusion of helium into carbon. This was demonstrated by Arthur Eddington using the Hertzsprung-Russell diagram.
  • #1
Maria76
14
0
Hi,

When the core of a star shrinks during its evolution, does it always lead to the expansion of the star? If not, why? What cases would cause it to expand?

Thanks in advance,
Maria
 
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  • #2
No, sometimes gravity from the mass of the star overcomes the energy from core fusion to shrink the star into a white dwarf about the volume of the Earth (which is held up by electron degeneracy) or a neutron star about the diameter of a city (which is held up by neutron degeneracy) or it collapses to a black hole.

http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html
http://imagine.gsfc.nasa.gov/docs/science/know_l1/neutron_stars.html
http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html

One case that causes it to expand is when the core fuses helium into carbon.

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971016.html

Arthur Eddington used the Hertzsprung-Russell diagram to demonstrate stellar physics.
http://en.wikipedia.org/wiki/Hertzsprung-Russell_diagram
 

1. What is star evolution?

Star evolution is the process by which a star changes over time, from its formation to its eventual death.

2. Does star evolution always lead to expansion?

No, star evolution does not always lead to expansion. The expansion or contraction of a star depends on its mass and the balance between internal pressure and gravity.

3. What factors influence the expansion of a star during evolution?

The main factors that influence the expansion of a star during evolution are its mass, composition, age, and environment. These factors affect the balance between internal pressure and gravity, which determines the size of the star.

4. Can a star shrink during its evolution?

Yes, a star can shrink during its evolution. This can happen when the internal pressure decreases, causing gravity to dominate and compress the star.

5. How does the size of a star affect its lifespan?

The size of a star directly affects its lifespan. Larger stars have shorter lifespans due to their greater energy output, while smaller stars have longer lifespans because they burn fuel at a slower rate. However, other factors such as composition and environment also play a role in the lifespan of a star.

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