Astrophysics

Question 1

describe what happens in a protostar

Answer 1

emits radiation
as density increases, pressure & temperature rise & more particles collide with each other
when the temperature is high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei
this gives out a lot of energy, which keeps the core of the star hot

Question 2

how is a white dwarf formed?

Answer 2

small/medium star gets unstable & ejects its outer layer of dust & gas, so only the hot, dense, solid core remains which is the white dwarf

Question 3

how is a black dwarf formed?

Answer 3

white dwarf cools down & emits less energy
when it no longer emits sufficient energy/radiation it is a black dwarf

Question 4

describe what happens before & in a supernova?

Answer 4

red super giants glow brightly & continues fusion, expanding & contracting several times
then it explodes in supernova
elements heavier than iron formed

Question 5

what is red-shift?

Answer 5

increase in wavelength of radiation so it is longer than the light emitted by the source
& shifted towards the red end of the spectrum
this happens when source of light is moving away from observer
it is evidence that galaxies are moving away from each other at an increasing rate (due to the doppler effect)
so the universe is expanding

Question 6

how does red-shift provide evidence for the big-bang?

Answer 6

light from further away galaxies is more red-shifted than light from nearer galaxies
shows galaxies are moving away from each other at an increasing rate & universe is expanding

then explain what big bang theory is:
theory that the universe began as a very small space that was very hot & dense, which exploded & been expanding ever since

Question 7

what is dark matter?

Answer 7

unknown substance that hold galaxies together & does not emit any electromagnetic radiation

Question 8

what is dark energy?

Answer 8

causes the accelerated expansion of the universe