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What is the star in our solar system?
The sun
What galaxy do we live in?
The milky way
How can we describe moons?
As a natural satellite which orbits around a planet
Where are stars formed?
From a cloud of dust and gas (nebula)
↳ hydrogen gas
Describe the stages of a star forming
Gravity causes the nebula to collapse
As dust particles moves faster, the temperature increases
This produces a protostar
When the temperature of the protostar gets high enough, hydrogen nuclei join to form helium (Nuclear fusion)
This forms a main-sequence star
Which 2 forces act on a star?
Gravity → causes the star to collapse
The force from nuclear fusion → causes the star to expand
What happens when the hydrogen in a star runs out?
The force of fusion energy is less than gravity so the star starts to collapse
What happens when a star collapses?
The temperature of the star increases
How is a red giant formed?
When a star collapses and starts to fuse helium nuclei together
How is a white dwarf formed?
When the fusion of helium in a star no longer occurs
Why does the white dwarf cool down?
Because it no longer carries out fusion
How is a black dwarf formed?
When a white dwarf stops releasing any energy
What happens to stars which are much bigger than our sun?
When they run out of hydrogen, they leave the main sequence stage and expand to form red super giants
What happens in a red super giant?
Helium nuclei fuse together to produce heavier elements
What is the limit of nuclear fusion for a main sequence star?
Any element heavier than iron
What happens when red super giants stop carrying out nuclear fusion?
The star explodes → supernova
How are elements heavier than iron formed?
In a supernova since the temperature is high enough to produce elements heavier than iron
What happens when a supernova explodes?
The elements within it are distributed throughout the universe
What can the explosion of a supernova form?
Neutron star → neutrons densely packed together
Black hole → Large gravity → light cannot escape
How does a planet stay in orbit?
Due to the force of gravity acting between the sun and Earth
What happens in a circular orbit to the velocity of an object?
The force of gravity leads to a change in velocity but not a change in speed
What happens when you increase the speed of a satellite? Why?
The radius of the orbit decreases
↳ Higher speed → requires a greater force of gravity
↳ Prevents the object from flying off into space
What happens to the wavelength of light as the distance between galaxies increases?
Increases
What does the red shift prove?
That galaxies are moving away from eachother
↳ Light waves are stretched → observed wavelengths have increased
How do we know which galaxies are moving faster away?
galaxies which are further away have a bigger red shift
How do we know that the galaxy is expanding?
Since distant galaxies are moving away faster than nearby galaxies
What can happen if a satellite moves too slowly?
Fall towards the Earth
↳ the gravitational attraction will be too strong
How can artificial satellites orbit?
Polar orbit (over the north and south pole)
Geostationary orbits → takes 24hrs to orbit the Earth
What does the Big Bang theory suggest?
The universe began from a very small region that was extremely hot and dense
