Space

Question 1

Life cycle of stars (Becoming a star)

Answer 1

Initially form a cloud of dust and gas (nebula)
Gravity pulls it together to make a protostar
Temperature rises as it gets denser with more collisions
Hydrogen will undergo fusion when it it hot enough to make helium nuclei, which gives out a lot of energy, keeping it hot

Question 2

Star stable period and what happens first after

Answer 2

Outward pressure caused by fusion balances the inward pulling gravity
Called a main sequence star and lasts several billion years
When it runs out of hydrogen it becomes a red giant or super giant depending on its side, red as the surface is cooler

Question 3

Red giant to end

Answer 3

It becomes unstable and ejects the outer layer of dust and gas
Leaves behind a hot, dense, solid core (white dwarf)
As it cools down it emits less and less energy. When it no longer emits a significant amount it is called a black dwarf

Question 4

Red super giant to end

Answer 4

Again glow brightly as they expand and contract as they undergo more fusion, forming elements as heavy as iron
Eventually they explode in a supernova, releasing element heavier than iron to form new planets and stars
Throws outer dust and gas into space leaving a very dense core called a neutron star. Some are so big they form an even denser black hole

Question 5

Solar system

Answer 5

Planets, orbit a sun, gravity strong enough to have pulled in all nearby objects except natural satellites
Dwarf planets orbit stars but don’t meet all the rules for a planet
Moons orbit planets- a type of natural satellite
Artificial satellites have been built by humans

Question 6

Orbits

Answer 6

Moving in a circle, constantly accelerating (change in velocity (direction) but not speed)
Inward force of gravity is at right angles to the acceleration so it continues circling

Question 7

What does the size of the orbit depend on

Answer 7

The closer you are, the stronger the gravitational force
Therefore it must move quicker to remain in orbit
If it is in a stable orbit, the radius of the orbit will change with the speed, faster moving objects have a smaller radius

Question 8

Red shift

Answer 8

Light from distant galaxies shows an increasing wavelength- towards the red end of the spectrum
Suggests the source is moving away very quickly
More distant galaxies have greater red shifts than near ones- suggests faster movement away
It would appear that the universe is expanding

Question 9

Big Bang theory

Answer 9

Galaxies are moving away, suggesting something must have started it, likely a big explosion (Big Bang)
Initially all matter occupied a very small space (very dense + hot)
Then it exploded- space started expanding and still is

Question 10

New evidence

Answer 10

Observations of supernovas suggest that they are moving away at increasing speed
Currently we think the universe is mostly made up of dark matter and energy, the unknown substance that holds galaxies together but emits no EM radiation
Dark energy is thought to be responsible for the rapid growth but we don’t really know what they are