P7 Page 16

Question 0

Describe the simple stages of a main sequence star becoming a neutron star or a black hole.

Answer 0

1) main sequence star
2) Red supergiant
3) mostly iron core
4) supernova
5) neutron star or black hole.

Question 1

Describe the simple stages of a star becoming a white dwarf.

Answer 1

1) Main sequence star
2) Red giant
3) white dwarf

Question 2

Describe in depth how a small star becomes a white dwarf.

Answer 2

1) when a main sequence star runs out of hydrogen to fuse, the core shrinks and the rest of the star expands, the photosphere cools. The star becomes a red giant.
2) The core shrinks until the pressure and temperature is high enough so that the star can fuse helium to make oxygen,carbon,nitrogen.
3) When the helium runs out the core is compressed by the res too the star.
4) a red giant does not have enough mass to compress the core, so more fusion occurs. The outer layers of the star are thrown off into space and the for shrinks to become a hot white dwarf, which cools and fades.

Question 3

Describe in detail how a main sequence star becomes a black hole or a neutron star.

Answer 3

1) when a main sequence star runs out of hydrogen to fuse, the core shrinks and the rest of the star expands, the photosphere cools. The star becomes a red giant.
2) The core shrinks until the pressure and temperature is high enough so that the star can fuse helium to make oxygen,carbon,nitrogen.
3) red supergiants do have enough mass to increase pressure(and temp) of the core enough to fuse larger nuclei.The red supergiant carries on fusing larger nuclei and its core keeps shrinking till most of the core has been fused into iron.
4) Red supergiant cannot fuse iron, so the core collapses and the star explodes as a supernova-creating nuclei with masses greater than iron.
5) Te core collapses to form a neutron star, or if there is enough matter a black hole.

Question 4

On the Hertzsprung-Russell diagram were are the main sequence stars, red giants and white dwarfs?

Answer 4

The white dwarfs have the highest temperature but the lowest luminosity.
The red giants and super giants have the lowest temperature but the highest luminosity.