The Solar System Flashcards
What is the geocentric model of the Solar System?
Put the Earth in the centre of everything with the planets and the Sun orbiting around it
What is the heliocentric model of the Solar System?
The Sun at the centre of the Solar System
What are asteroids?
Compromised of rock and metal and are smaller than planets, most of which are found between the orbits of Mars and Jupiter
What are comets?
Frozen leftovers from the formation of the Solar System composed of dust, rock and ice that orbit the Sun
What is an elliptical orbit?
The orbit of an object around another in an oval-shaped path, such as the orbit of planets around the Sun in our Solar System
Give an example of a natural satellite
Moon
Why do telescopes in orbit around the Earth give much clearer images than ground-based telescopes?
Clouds and dust in the air do not interfere with the image
Why must telescopes that are used to detect different types of EM waves be placed in orbit?
Because the atmosphere absorbs some of the radiation they are designed to detect
What is weight?
The force of gravity acting on matter
What does weight depend on?
Mass and GFS
What are artificial satellites used for?
Communications and observation of the Earth and space
Why does an orbiting body constantly change velocity?
In a circular orbit, it has a constant speed as it travels, but its direction is constantly changing
For a satellite, how does the force change its direction but not its speed?
The gravitational force between the Earth and the satellite is at right angles to the direction of movement (centripetal force)
What is a nebula?
A cloud of dust and gases (mainly hydrogen)
What is the life cycle of an average star?
- Stellar nebula (cloud of gas)
- Average star
- Red giant
- Planetary nebula
- White dwarf
What is the life cycle of a massive star?
- Stellar nebula (cloud of gas)
- Massive star
- Red supergiant
- Supernova
- Black hole or neutron star
Describe the formation of a star
- Nebula’s materials pulled together by their own gravity
- Clouds contract and become denser
- Hydrogen heats up and spirals inwards and may start to glow
- As more mass is attracted, cloud’s gravitational pull strengthens and heats the material even more, which becomes a protostar
- Temperatures and pressures in centre of protostar become high enough to force hydrogen nuclei to fuse together and form helium (fusion reaction releases a lot of energy as EM radiation)
- Outward pressure from hot gases balances the compression due to gravity
- Star now in the main sequence part of its life-cycle
What is the Doppler effect?
The apparent difference between the frequency at which sound/light waves leave a source and that at which they reach the observer
Give an example of the Doppler effect
As an ambulance siren travels away from you, its pitch gets lower
What happens to the sound waves behind a moving sound source?
They become ‘stretched’, which makes their wavelength longer; this in turn lowers their frequency and so we hear the sound as a lower pitch
What happens if you are travelling in a car with the same velocity as the vehicle with the siren in terms of the Doppler effect?
The sound would not appear to change
What is the red shift?
When the wavelength of light is ‘stretched’, the light is seen as shifting towards the red part of the spectrum (happens when a star is moving away from us)
What is the red shift a measure of?
How far along the spectrum lines have moved
What happens to the wavelength of light waves when a star is moving towards us?
The waves become shorter and the frequency increases, so the pattern of lines moves towards the blue end of the spectrum
What does it mean when the further the lines are shifted in the visible spectrum of light?
The faster the star is moving relative to us
What is the relationship between a galaxy, its red shift and its distance from us?
The further away a galaxy is, the greater its red-shift and so the faster it is moving away from us
What caused matter to clump together to form stars as the Universe expanded during the early stages after the Big Bang?
Gravity
What does the Steady State theory suggest?
The Universe has always existed and is expanding; new matter is continuously created within the Universe as it expands
What does the Big Bang theory suggest about radiation?
Huge amounts of radiation were released at the beginning of the Universe
What is happening to the radiation released from the Big Bang as the Universe expands?
The wavelength of this radiation has increased and so now it is only detectable as microwave radiation
What is cosmic microwave background (CMB) radiation?
The radiation from the beginning of the Universe whose wavelength has increased as the Universe expanded to only be detected as microwave radiation
What do the Big Bang and Steady State theories have in common?
Both say that the Universe is expanding
What can be used as support for the Big Bang and Steady State theories?
Observations of red-shift in the light from other galaxies
What does CMB radiation provide evidence for?
The Big Bang theory only, as the Steady State theory cannot explain the CMB radiation
Which theory for the Universe is accepted by most astronomers today?
The Big Bang theory, as there is more supporting evidence for it
