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.
SP7e - What is the Steady State Theory?
The universe always existed and as it expands matter is continuosly created.
SP7e - Which theory of the universe is the currently accepted theory?
The Big Bang Theory
SP7e - What provides evidence for both theories of the universe and why?
Red-shift; as galaxies are constantly moving away the universe is constantly expanding.
SP7e - What provides evidence for the currently accepted theory.
CMBR (Cosmic Microwave Background Radiation) is found throughout all of the universe at the same rate suggesting that it all started form one point and expanded out from there.
SP7e - What can we use as a model of why CMBR proves The Big Bang Theory?
- A Currant bun has currants close together.
- As the dough rises, the number of currants stay the same but they are found at consistent rate throughout the bun.
SP7d - What does it mean if one galaxy has a greater red-shift than another?
That galaxy is further away and moving faster than the other.
