space physics - paignton community and sports academy · an “asteroid belt” lies between mars...
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Space Physics
AQA Physics topic 8
8.1 Solar System, Orbits and Satellites
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21/11/2017 The eight planets of our Solar System
Mercury
Mars
Jupiter Saturn
Neptune
Uranus
Venus Earth
As well as the eight planets, the solar system is also made up of asteroids, dwarf planets, comets and moons
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Asteroids
An “asteroid belt” lies between Mars and Jupiter. But what is an asteroid?
21/11/2017 Comets Comets are balls of dust and frozen gas. They have very elliptical orbits:
Notice how the tail always points away from the sun!
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The Solar System summarised What makes up our solar system? Complete the following mind map with what you now about each object:
The solar system
21/11/2017 Solar systems, galaxies and the Universe
OUR SUN (100 times wider), which is small compared to…
THE MILKY WAY, which contains at least 200 billion stars, which is small compared to…
Our planet (around 13,000km diameter) is pretty small compared to...
THE UNIVERSE, which contains billions of galaxies.
Nuclear Fusion vs Nuclear Fission 21/11/2017
Nuclear fission happens in power plants and nuclear bombs – it’s basically “splitting a nucleus”. Nuclear fusion happens in stars – it’s basically “fusing nucleii together”
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The Life Cycle of a Star
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Stage 1: Nebulae
A nebulae is a collection of dust, gas and rock.
Some examples of nebulae…
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Dark nebula
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Emission nebula
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Reflection nebula
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Planetary nebula (This nebula is smaller and will only form a planet)
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Gravity will slowly pull these particles together…
As they move inwards their gravitational potential energy is converted into heat and a PROTOSTAR is formed
Stage 2: Protostar
21/11/2017 Stage 3: Main Sequence
Our sun is an example of a main sequence star – it’s in the middle of a 10 billion year life span
In a main sequence star the forces of attraction pulling the particles inwards are _________ by expansion forces due to nuclear ______ reactions and the high temperature.
Stars are basically ________ reactors that use _______ as a fuel. During its main sequence a star will release energy by converting hydrogen and helium (light elements) into _________ elements and this is why the universe now contains a number of heavier elements.
Words – heavier, balanced, hydrogen, nuclear, fusion
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Nuclear Fusion in stars Proton Neutron
Nuclear fusion happens in stars and leads to the formation of new elements. It’s not possible to use it in power stations yet as it needs temperatures of around 10,000,000OC and
seriously high pressure.
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Eventually the hydrogen and helium will run out. When this happens the star will become colder and redder and start to swell…
If the star is relatively small (like our sun) the star will
become a RED GIANT
If the star is big (at least 4 times the size of our sun) it will become a
RED SUPERGIANT
Stage 4: Red Giant
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What happens at this point depends on the size of the star…
1) For SMALL stars the red giant will collapse under its own gravity and form a very dense white dwarf:
Stage 5: The Death
White dwarf Black dwarf Red giant
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2) If the star was a RED SUPERGIANT it will shrink and then EXPLODE, releasing massive amounts of energy, dust and gas.
After Before
This explosion is called a
SUPERNOVA
Stage 5: The Death
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The dust and gas on the outside of the supernova are thrown away by the explosion and the remaining core turns into a NEUTRON STAR.
If the star is big enough it could become a BLACK HOLE instead.
Stage 5: The Death
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The dust and gas thrown out by a supernova can be used to form a new star…
Stage 6: Second generation stars
Our sun is believed to be a “______ ______ star” – this is because it contains some __________ elements along with hydrogen and ________. These heavier elements would have been produced by a ____________ and thrown out when the star exploded. These heavier elements are also found on planets, indicating that they might have been made from remains of previous _______ as well.
Words – helium, heavier, second generation, stars, supernova
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The Life Cycle of a Star summary Protostar
Main sequence
Red super giant
Supernova
Red giant
White dwarf
Black dwarf Neutron star Black hole
Basically, it all depends on the size of the star!
SMALL stars
BIG stars
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The Earth’s Orbit
Ellipse
Gravity keeps us in orbit around the sun. How long does this orbit take?
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Circular Motion recap
1) Is this car travelling at constant speed?
2) Is this car travelling at constant velocity?
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The Moon’s Orbit Gravity also keeps the moon (a natural satellite) in orbit around us. How long does this take?
Does the moon travel at constant speed? Does it travel at constant velocity?
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Satellite orbits Gravity also keeps artificial satellites in orbit around us.
Q. What would have to happen to the satellite’s speed if it moved closer to the Earth?
A. As the orbital radius INCREASES the speed of the satellite will DECREASE.
8.2 Red Shift 21/11/2017
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How did the universe begin?
The Big Bang Theory suggests that the universe began from a very small region that was very hot and dense, and then…
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How did the universe begin?
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Source of light “Spectra”
Evidence for the Big Bang Theory
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If you pass the light through a gas something different is seen…
helium
Some wavelengths of light are absorbed by the gas – an “absorption spectrum”.
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After
helium
If the light source is moving away the absorption spectra look a little different…
helium
Before
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The absorption lines have all been “shifted” towards the longer wavelength end (red end)…
After
Before
A similar effect happens with sound – this is called “The Doppler Effect”
This is called red shift. The faster the light source moves the further its light will be “shifted”
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Red Shift simplified
Basically, if I walk towards you I’ll look slightly more blue. Then, if I walk away
from you, I’ll look slightly more red!!
Let’s try it…
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Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point.
This is the BIG BANG theory
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Red shift summary Light from other galaxies has a longer _________ than expected. This shows that these galaxies are moving ____ from us very quickly. This effect is seen to a greater extent in galaxies that are _______ away from us. This indicates that the further away the galaxy is, the ______ it is moving.
Words to use – faster, away, big bang, billion, wavelength, further, supernovae
This evidence seems to suggest that everything in the universe is moving away from a single point, and that this process started around 14 _____ years ago. This is the ____ ________ Theory. Observations of ________ from 1998 onwards have suggested that distant galaxies are receding even faster.
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Dark Mass and Dark Energy 21/11/2017
No Mr President! There is still loads of stuff we don’t know about the universe, such as dark mass and dark energy.
So, does this mean that we now know everything about the universe?