Space

Question 1

Explain the formation of a star until a red giant.

Answer 1

1. Gravity pulls dust and gas together from a nebula to form a protostar
2. The temperature rises as the star gets denser until hydrogen nuclei undergo fusion to form helium, keeping the star hot
3. The star reaches a stable point where the outward pressure caused by fusion balances the force of gravity - this is a main sequence star
4. Eventually the hydrogen runs out and the surface cools, becoming red and heavier elements form in the core of the star (red giant or red super giant)

Question 2

Explain the life of a small/ medium star after red giant

Answer 2

1. The red giant becomes unstable and ejects its outer layer of dust and gas, forming a white dwarf, a hot dense core
2. The white dwarf cools down and emits less energy, becoming a black dwarf

Question 3

Explain the life of a big star

Answer 3

1. The super red giant will undergo more fusion of heavier elements until it explodes into a supernova, ejecting heavy elements into the solar system
2. The supernova leaves behind a dense core called a neutron star which, if massive enough, will become a black hole

Question 4

What determines a planet?

Answer 4

If it can clear its neighbourhood, their gravity can pull in any nearby objects

Question 5

Explain forces in an orbit

Answer 5

1. An object travelling in a circle is constantly changing velocity and accelerating
2. Gravity causes the object to accelerate as the object is moving it also causes it to change direction
3. The object keeps accelerating towards what it is orbiting but the instantaneous velocity keeps it travelling in a circle

Question 6

How does speed affect the size of an orbit?

Answer 6

1. The closer to a planet, the stronger the gravitational pull
2. The stronger the force, the faster the object needs to travel
3. In a stable orbit if the speed of the object changes it must adjust its radius to suit the gravitational pull of the planet

Question 7

How does red shift indicate that the universe is expanding?

Answer 7

1. Absorption lines from light from distant galaxies has increased wavelengths
2. They have shifted towards the red end of the spectrum
3. This suggests the source of light is moving away from us
4. Distant galaxies are moving away faster than nearer ones

Question 8

Explain the big bang

Answer 8

1. Initially all matter in the universe occupied a very small space which was very dense and very hot
2. Then it exploded and expanded, so the expansion is still happening