Astronomy Flashcards
What does The Big Bang Theory state about the universe?
- That it started as a tiny particle about 13.8 billion years ago
- It expanded from this point in space
- It is still expanding today
- Same amount of matter, none created or destroyed
- Density of matter decreases over time
What does the Steady State Theory state about the universe?
- It has always existed
- It is still expanding
- New matter is continuously created as it expands
- Density of matter stays constant over time
How does Redshift suggest that the universe is expanding?
- When objects that emit light are moving away from us, the light they emit is red shifted
- This means the wavelengths from them when detected back on Earth will be ‘stretched’
- The spectral lines will be shifted to the red end of the spectrum
- The faster the galaxy is travelling away from us, the more these lines will be shifted to the red end of the spectrum
- As the furthest galaxies show more red shift than those nearer to us, the universe must be expanding
How does cosmic microwave background radiation support The Big Bang Theory?
- CMB comes from all directions in space and has a temperature of about -270°C
- CNB is the remains of the thermal energy from the Big Bang, spread thinly across the whole universe
What is the Doppler effect?
When a wave source is moving relative to an observer there is a change in the observed frequency and wavelength of the waves
How can the speed of the Galaxy be determined from the absorption lines in its spectrum?
- Absorption lines in the spectra of the light from the galaxy can be compared with the corresponding absorption lines of a stationary source
- The difference in the position/wavelength/frequency can be used to calculate the speed of the galaxy
What is the order of the eight planets from the Sun?
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
What is an exoplanet?
A planet outside of our solar system
What was the geocentric model?
- Ptolemy, Greek astronomer
- Earth was the centre of the universe
- Planets also moved in little circles as they moved around earth
What was the heliocentric model?
- Copernicus
- Earth and six planets went around the Sun
What are some examples of natural satellites?
- Planets
- Moons
- Comets
What are some examples of artificial satellites?
- Satellites in geostationary orbit - used for GPS
- Satellites in low polar orbits - used for weather monitoring, military, spying, and earth observation purposes
- Satellites sent from Earth to orbit and monitor the Sun 
What are the stages of the life-cycle of a low mass star?
- Nebula
- Protostar
- Main sequence star
- Red giant star
- White dwarf
- Black dwarf
What are the stages of the life-cycle of high mass stars?
- Nebula
- Protostar
- Main sequence star
- Red supergiant star
- Supernova
- Neutron star/black hole
What is a nebula?
A cloud of dust and hydrogen gas
How is protostar formed?
- Gravity pulls the nebula together
- As the dust and gas contracts, the nebula gets hotter as work is being done on it
- When it is hot enough, the hydrogen nuclei fuse together to make helium
- The fusion process releases energy which keeps the core of the star hot
Why is a main sequence star stable?
The inward force of gravity is balanced by the outward force of thermal expansion
How is a red giant star formed?
When most of the hydrogen gas has been used up by fusion, larger nuclei begin to form and it will expand
How is a white dwarf formed?
All nuclear fusion stops and the star collapses
What causes a supernova?
- Larger stars continue making nuclear reactions, getting hotter and expanding until they explode
- This releases hot gas into space
How are neutron stars and black holes formed?
- If the remains of a supernova are less than 4x the mass of the Sun, gravity pulls it together to form a small dense star (neutron star)
- Larger stars collapse completely and vanish as light cannot escape its gravity
