Space Physics (Paper 2)

Question 1

Stage 1 in the lifecycle of a star

Answer 1

• Stars initially form from a cloud of dust and gas called a nebula

Question 2

Stage 2 in the lifecycle of a star

Answer 2

• The force of gravity pulls the dust and gas together to form a protostar
• Temperature rises as the star gets denser
• When the temperature gets high enough hydrogen nuclei undergo fusion to form helium nuclei
• Fusion releases lots of energy which keeps the core hot
• A star is born

Question 3

Stage 3 in the lifecycle of a star

Answer 3

• The star enters a long stable period where the outward pressure caused by the nuclear fusion that tries to expand the star balances the forces of gravity pulling everything inwards
• The stable period is called a main sequence star and typically lasts for several billion years

Question 4

Stage 4 in the lifecycle of a star

Answer 4

• Eventually the hydrogen begins to run out. The star then swells into a red giant or a red super giant
• It becomes red because the surface cools
• Fusion of helium occurs
• Heavier elements up to hydrogen are formed in the core of the star

Question 5

Stage 5 in the lifecycle of a small to medium sized star

Answer 5

• Becomes unstable and ejects its outer layer of dust and gas
• This leaves behind a hot, dense, solid core known as a white dwarf

Question 6

Stage 6 in the lifecycle of a small to medium sized star

Answer 6

• As a white dwarf cools down, it emits less and less energy
• When it no longer emits a significant amount it is called a black dwarf

Question 7

Stage 5 in the lifecycle of a large star

Answer 7

• They start to grow brightly again as they undergo more fusion and expand and contract several times
• Eventually they will explode forming elements heavier than iron and ejecting them into the universe to form new planets and stars

Question 8

Stage 6 in the lifecycle of a large star

Answer 8

• The exploding supernova throws out the outer layers of dust and gas into space, leaving a very dense core called a neutron star
• If the star is massive enough it will become a black hole

Question 9

Define planets

Answer 9

• Large objects that orbit a star

Question 10

Define dwarf planets

Answer 10

• Planet-like objects that orbit stars but don’t meet all the requirements to be a planet

Question 11

Define moons

Answer 11

• Natural satellites that orbit planets

Question 12

Define artificial satelites

Answer 12

• Human made satellites

Question 13

Define galaxy

Answer 13

• A massive collection of billions of stars that are held together by gravity

Question 14

Describe the shape of orbit of the planet around the sun

Answer 14

• Almost circular

Question 15

What is the relation between the speed of the object and size of orbit

Answer 15

• For an object in stable orbit, the faster the orbit the closer the object to the object being orbited