Astronomy Flashcards
(16 cards)
Who came up with the geocentric model?
Ptolemy
Describe the geocentric model
This suggests that the sun, the moon and the planets orbited the Earth in perfect circles. They believed this because they saw the sun and moon in the sky everyday at similar times.
Who came up with the heliocentric model?
Nicolaus Copernicus
Describe the heliocentric model
This suggests that all the planets orbited around the sun in perfect circles.
What did Galileo prove?
By seeing the moons around Jupiter he saw a line of stars. When he looked through the telescope he saw that Jupiter had moved but the star didn’t. This shows not everything was in orbit around the Earth.
Describe the current model
It is the same as the heliocentric model however, the planets orbit in elliptical (slight squished) orbits.
Describe the steady state theory
It suggests that the universe has always existed as it does now and will continue to exist. It also says that the universe is the same everywhere and as the universe expands, new matter is constantly being made. Therefore, the density of the universe is the roughly the same.
Describe the Big Bang
It suggests that at the beginning all matter in the universe stayed in a very small space / point. This space was very hot due to it being very dense and then exploded. After this, space starting expanding and still is today. This happened 13.8 billion years ago.
Explain the doppler effect
When waves from a stationary source is emitted, the waves are equally spread out therefore the frequency and wavelength is the same. However if the source is moving towards you the waves at the front of the bunch up and the frequency is high and the wavelength is shorter. This also happens when its moving away when it is moving away the waves spread out and the wavelength increases as the frequency decreases.
Explain CMB (cosmic microwave background radiation)
This supports the the Big Bang Theory. Scientists found low frequency electromagnetic radiation coming from everywhere in the universe which is mainly in microwave (EM spectrum.) They believe that it is leftover energy from the explosion.
What is the sequence that normal sized stars go through?
Nebula -> Protostar -> Main sequence -> Red giant -> White dwarf -> Black dwarf
What is the sequence that stars much bigger that the sun goes through?
Nebula -> Protostar -> Main sequence -> Red supergiant -> supernova -> neutron start / black hole
Explain the sequence of all stars
- They start as a nebula (cloud of dust and gas)
- Gravity pulls the nebula together to form protostar
- It gets denser and more particles collide when the temperature rises
- When hot the nuclei will undergo nuclear fission to for a helium nuclei
- This gives out huge amounts of energy
- A star is born and enters a long stable period
- During this the force of gravity holding the star together is balanced by the higher pressure sue to high temperature
- When all the hydrogen has been used up a large nuclei forms allow the star to expand into a red giant or supergiant.
What happens after a star forms into a red giant?
- When all the reactions are done and the star becomes unstable it ejects its outer layer of dust and gas.
- This leaves a hot and dense solid core: a white dwarf
What happens after a star forms a super red giant?
- They begin to glow brightly as it goes through more fusion
- They will continuously expand and contract as the balance changes between gravity and thermal.
- It will then explode into a supernova
- It will either explode and throw all its outer layers of dust and gas leaving a dense neutron star
- Or it can leave a supernova collapsing and becoming a black hole, a very dense point in space that even light cannot escape , if the star is massive enough.
What is red shift?
- its suggests that universe is expanding
- different elements absorb different frequencies of light
- this creates a specific pattern of dark lines
