P16

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What are comets?
Frozen rocks that move around the sun in orbits that are elliptical in shape
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When do you see comets?
When they return near the Sun because they heat up so much that they emit light
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What are meteors or shooting stars?
Small bits of rock that burn up when they enter the earth's atmosphere
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What is the first step in the creation of the sun?
Clouds of gas, rocks and dust span
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What is the second step in the creation of the sun?
The sun formed at the centre of all of these because of the force of gravitational attraction
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What is the third step in the creation of the sun?
The sun's heat evaporated ice and drove gas away from the inner solar system, leaving rocks behind
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What is the fourth step in the creation of the sun?
The rocky planets near the sun and the gas giant planets formed further away.
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What is a protostar?
When the clouds merge together
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What happens as a protostar becomes denser?
Its particles speed up, collide more so temp increases and it gets hotter
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What happens if the protostar becomes hot enough?
The nuclei of hydrogen atoms fuse together forming helium nuclei
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What is released in this fusion?
Energy so protostar gets hotter, brighter and starts to shine
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What happens to objects that are too small to become stars?
They can become planets orbiting the star
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What are main sequence stars?
Stars that can maintain their energy output for millions of years
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What keeps the core hot and continues the process of fusion?
The fact that energy is released in the core
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Why is the star stable?
Because the forces within it are balanced
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What are the forces within?
The force of gravity acts within and tries to make the star contract but this is balanced with the outward force of radiation from nuclear fusion in the core trying to make core expand
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How long do these forces stay in equilibrium?
Until most of hydrogen nuclei in core have been fused together to form helium nuclei
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What is the heaviest natural element?
Uranium
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What does the presence of uranium show?
The solar system formed from the remnants of a supernova
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How can scientists make heavier elements?
By bombarding heavy elements with high speed neutrons
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After all nuclei have fused what happens to stars bigger than the sun?
They swell out and become red supergiants, then collapse. The matter surrounding the stars core compresses the core more then explodes in a supernova
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After all the nuclei have fused what happens to stars same size or smaller than sun?
Turn to red giants, at this stage helium and other light elements in core fuse to form heavier elements. When no more light elements star collapses. Heats up and turns from yellow - white. This is a white dwarf
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What is a white dwarf?
A hot, dense star much smaller in diameter than it was before
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What happens next?
Cool down and become a black dwarf
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What is the highest nuclei that can be formed?
Nuclei larger than iron nuclei because too much energy required
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When are heavier elements formed?
When a massive star collapses then explodes e.g. a supernova
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What happens after a suprernova?
Explosion compresses core into a neutron star then if big enough it will become a black hole
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What are the properties of a black hole?
Gravitational field strength is so strong nothing can escape, not even light
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What is the centripetal force?
A force that acts towards the centre of a circle
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What changes the velocity of a planet during orbit?
Changed by the centripetal force
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What is the direction of motion of any planet in a circular orbit?
At right angles to the direction of the force of gravity
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Why does a planet experience acceleration towards the centre of the circle?
Because the resultant force (gravity) acts towards the centre
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Does the speed of a planet in a circular orbit change?
No
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Why do satellites in orbits too close to the earth gradually lose speed?
Because of atmospheric drag if orbit is in upper atmosphere. If a satellite loses speed it gradually spirals inwards until hitting the earth
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A satellite in a circular orbit above earths atmosphere moves around the earth at what?
A constant height above it
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What does a satellite have to do to stay in orbit of a particular orbit?
Satellite has to move at a particular speed around earth
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For any small body to stay in circular orbit around another bigger orbit what must happen?
The smaller body must move at a particular speed around the bigger body
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The further a satellite is from the earth what?
The less the particular speed needed for it to stay in a circular orbit. The force of gravity is weaker and does not need to travel as fast
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Another.
The longer the orbiting body takes to move around the orbit once, circumference of orbit is bigger
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What is the formula for the time taken for a complete orbit?
Circumference / speed
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What are geostationary orbits?
They orbit the earth in the same direction as the earths spin, stay above same place on earths surface
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What is a galaxy?
An enormous collection of stars that stay together because of gravity
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If a star or galaxy is moving away what happens to the light waves?
They are stretched out
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What happens to the wavelengths if moving away?
They increase
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Why is this called a red-shift?
Because the spectrum of light is shifted towards the red part of spectrum
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What happens to the light waves and their wavelnegth if it is moving away?
They are squashed together and wavelength is reduced
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Why is this called a blue-shift?
Because the spectrum of light is shifted towards blue part
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What are the dark spectral lines?
They are caused by the absorption of light by specific atoms e.g.hydrogen
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What does the position of these lines tell you?
If there is a blue shift or red shift
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The faster a star is moving, the bigger the what?
The shift
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The greater a galaxy is from earth the greater the what?
The speed at which its moving away
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Why do distant galaxies move away?
Because universe is expanding
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What is the big bang theory?
That the universe is expanding after exploding suddenly from a very small and extremely hot and dense region
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What were created in the big bang?
Space , time and matter
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What is the other theory that disagrees with the big bang theory?
The steady state theory that states galaxies are being pushed apart because matter entered universe through a white hole
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How did they prove the big bang theory was better than steady state?
Worked out electromagnetic radiation would have been produce so detected CMBR
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What does CMBR stand for?
Cosmic microwave background radiation
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What is CMBR?
Created as high energy gamma radiation but travelled through space so is now microwave radiation
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What is dark matter?
Cant be seen, average density of universe is much bigger with it
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If the density of the universe is less than a particular amount what happens?
It will expand forever until stars die out (Big Yawn)
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If the density of the universe is more than a particular amount what will happen?
Stop expanding and go into reverse (Big Crunch)
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Other cards in this set

Card 2

Front

When do you see comets?

Back

When they return near the Sun because they heat up so much that they emit light

Card 3

Front

What are meteors or shooting stars?

Back

Preview of the front of card 3

Card 4

Front

What is the first step in the creation of the sun?

Back

Preview of the front of card 4

Card 5

Front

What is the second step in the creation of the sun?

Back

Preview of the front of card 5
View more cards

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