Topic 7 - Astronomy Flashcards
SP7a - What is the geocentric model?
The model of our solar system in which everything orbits the earth.
SP7a - What is the heliocentric model?
The current model of our solar system where the sun is at the centre and other planes orbit it.
SP7a - What shape is the earth’s orbit around the sun?
Elliptical
SP7a - What developments in techonology have allowed us to make more detailed observations?
- Computers allow detailed analysis.
- Photography allows accurate and permanent storage of events.
- Telescopes can now be place outside of the earth’s atmosphere giving wider and more detailed detection.
- Space probes allow better analysis of the solar system.
SP7a - Why are telescopes place outside the earth’s atmosphere more detailed than a regular telescope?
- The earth’s atmosphere absorbs many waves of the EM spectrum.
- Outside the atmosphere, these could be detected. (such as infrared radiation)
SP7b - What is the difference between weight and mass?
Your weight is the force acting on you dependant on your mass and the gravitational field strength.
SP7b - What is the gravitational field strength on earth?
9.81 N/Kg
(Can be rounded to 10N/Kg)
SP7b - What are the four types of orbits for artificial satellites?
- Highly elliptical
- Circular geostationary
- Low earth orbits
- Polar orbits
SP7b - What is a geostationary orbit and what are these satellites used for?
- Satellites that stay in the same place relative to the earth’s position.
- They move at 3070 m/s and are used for broadcasting.
SP7b - A satellite in which type of orbit will eventually pass over all parts of the earth?
Polar orbits
SP7b - A satellite in which type of orbit needs the least fuel for launching?
Low earth orbits
SP7b - A satellite in which type of orbit is used for communication with parts of the earth near the poles?
Highly elliptical orbits
SP7b - Why doesn’t a satellite continue moving in a straight line?
The gravitational force between the earth and the satellite causes it to continuously change direction and orbit the earth.
SP7b - At what angle is the force between the earth and satellite?
90°
SP7b - Explain the speeds that a satellite would have to be travelling at in relation to its orbit, and the changes in orbit it would experience if it changed speed.
- The gravitational force on an object in a lower orbit is a stronger than at a higher orbit so a satellite at a lower orbit would have to travel at a higher speed to stay in orbit.
- Once it eventually slows down, it will drop towards earth.
- However as it drops it gains speed and will eventually be able to be at a lower orbit at a faster speed.
- Once it drops enough that it passes through the earth’s atmosphere, the air resistance will slow it down and it will eventually fall to earth.
SP7b - What reaction takes place inside a star?
Nuclear fusion
(typically H + H = He)
SP7b - Describe the life cycle of a star the size of our sun. [6 Marks]
- It starts with a Nebula (A cloud of gas).
- The particles in this pull themselves together, becoming denser until their own gravity causes it to collapse in on itself forming a protostar.
- Eventually the pressure and temperature in the protostar become large enough that nuclear fusion starts to occur converting hydrogen to helium
- The energy released form the fusion reactions push the star outward causing it to expand.
- Once the force of the gravity pulling the star inwards matches the force of pressure from the fusion reactions, the star will be at a steady size and in its main sequence stage where it continues to convert hydrogen to helium
- Eventually, hydrogen runs out and heavier reactions take place.
- This creates more energy which expands the star more
- The outermost layers are no longer held in place by the force of gravity so they expand forming a red giant
- Once all the fuel has run out, all the layers disband forming a shell of gas.
- This leaves behind a highly dense white dwarf which doesn’t carry out any reactions.
SP7b - Describe the life cycle of a star much larger than our sun. [6 Marks]
- It starts with a Nebula (A cloud of gas).
- The particles in this pull themselves together, becoming denser until their own gravity causes it to collapse in on itself forming a protostar.
- Eventually the pressure and temperature in the protostar become large enough that nuclear fusion starts to occur converting hydrogen to helium
- The energy released form the fusion reactions push the star outward causing it to expand.
- Once the force of the gravity pulling the star inwards matches the force of pressure from the fusion reactions, the star will be at a steady size and in its main sequence stage where it continues to convert hydrogen to helium
- Eventually, hydrogen runs out and heavier reactions take place.
- This creates more energy which expands the star more forming a red supergiant.
- These heavier fusions are carried out all the way to iron when it runs out of fuel.
- The star rapidly collapses causing a supernova
- This leaves behind a very dense neutron star
- If the mass of the star is even larger, then a black hole is formed in place of the neutron star.
SP7d - What is the doppler effect?
When the pitch of a noise get lower as it travels aways from you. (and higher when it travels towards you)
SP7d - Why does the doppler effect occur?
As a sound travels, the wavelengths are squashed or stretched meaning the sound’s pitch appears higher or lower.
SP7d - What is red-shift?
When light form distant galaxies shift towards the red side of the spectrum due to wavelengths being stretched as the galaxy moves away from earth.
SP7d - What do we use to check red-shift?
Absorption spectrums of the galaxy compared to the absorption spectrum of the sun.
SP7e - What are the two main theories for the origin of the universe?
- The big bang theory
- Steady state theory
SP7e - What is the Big Bang Theory?
- The whole universe started out from one point of concentrated energy.
- All matter started form this point and continued to expand outwards as the universe constantyl expands.
