Space Flashcards
(19 cards)
How do astronomers think the solar system was formed?
4,500 million years ago a shock wave triggered the collapse of a gas cloud into a doughnut shape which flattened out.
Enough hydrogen gathered in the centre for fusion to start in the Sun, solid particles began to strike each other and stick together, this debris eventually formed planets and their moons.
Eventually most of the gas and dust in the solar system became attached to a planet, left over dust and frozen gases formed the comets.
What are the four inner planets?
Mercury, Venus, Earth and Mars.
These are called rocky planets with solid surfaces.
What are the four outer planets called?
Jupiter, Saturn, Uranus and Neptune are larger than the other four and are called gas giants planets.
They are thought to consist of mainly gas.
Pluto is a dwarf planet and has a rocky surface and is the same size as our moon.
The planets orbits are elliptical in shape.
What does the force of gravity depend on?
The mass of the objects and the distance between them.
If the mass is doubled, the force is doubled (they are directly proportional).
If the distance is doubled, the force is quartered (this is an inverse square law).
What does the suns gravity do to comets?
When they are close to the sun, the force of gravity increases and they speed up, they are made of a frozen mixture of ice and dust.
The solar radiation head the ice and vaporises it, the dust particles are pushed away from the comet by solar radiation pressure, this means the comet’s dust tail always points away from the sun.
Planetary and satellite movement in orbit
The force of gravity holds the planets in orbits around the sun and also satellites and moons as they orbit the planets, as the planets/satellites move around their orbit the gravitational force provides the circular motion force to keep them in orbit.
Satellites are placed at different distances from the Earth depending on how quickly we want them to orbit and what they want them to do.
What are geostationary satellites?
Are positioned so that they orbit at the same speed that the Earth is rotating, meaning they stay above the same point on the Earth all the time.
24 hour orbit, need to be positioned far out.
Uses - weather, communication + TV and surveillance.
What is a low polar orbit satellite?
Close, low level orbit.
90 min orbit.
Orbits around the poles.
Can scan whole Earth.
Uses - weather, surveillance and telescopes.
What is a light year?
One light year is the distance travelled by light in one year
How to calculate one light year?
Speed X Time.
Time is seconds in a year.
What is a galaxy?
Large group of stars held together by gravity
What is the nearest star in our galaxy?
Alpha Centauri and is 4.3 light years away.
Diameter of the milky way (our galaxy) is 100000 light years.
What is the red-shift?
Astronomer called Hubble discovered that the light coming from stars appeared to have shifted on the spectrum from where is should have been, more to the red end of the spectrum.
Explanation is that if the stars and galaxies we can see from Earth were moving away from us (Universe is expanding).
This discovery supported the suggestion that everyone was once much closer together and therefore supports the big bang and suggests that the stars and galaxies are still moving as a result of the Big Bang.
What is cosmic microwave background radiation? (CMBR)
Discovered in 1965 by astrophysicists testing a microwave antenna and was initially thought to be caused by pigeon poo.
They discovered that a physicist, Robert Dick, had hypothesised that low level microwave radiation should exist and was the ‘after glow’ of the heat from the Big Bang, resonating through the universe, they had just found it and CMBR is the only explanation.
How does Hydrogen and Helium help explain the Big Bang?
The amount in the universe is consistent with the massive fusion reactions which occurred in the very early stages of the Big Bang.
There is too much Helium for it to have made in stars since the Big Bang, the amounts are currently only explained by the Big Bang.
How does a star start out?
Over millions of years clouds of gas mostly hydrogen and helium called nebulae, drift in space and are pulled together by gravity.
As the gas forms into a ball the temperature rises and the ‘infant’ star begins to give out infrared radiation.
How does a star become balanced? (Main sequence)
The temperature and pressure in the centre builds up until it becomes possible for the hydrogen nuclei to fuse together to make helium, this is called nuclear fusion and is a very powerful form of energy release which produces vast amounts of heat.
The radiation given off from nuclear fusion pushed outward against gravity and prevent further collapse of the star, once formed the star will undergo fusion until it runs out of fuel.
In a stars life it was have a balanced system where radiation pressure = gravitational force.
What happens when a star dies?
Most stars die peaceful deaths, but if it has a large mass then it will become a RED SUPERGIANT before the central core collapses to produce a shock wave which makes the outer layers explode.
This type of violent end is called a SUPERNOVA and releases a sudden outburst of energy, 10 billion times brighter than the sun for a short period.
What things could happen after supernova?
- The cord may continue to collapse under its own gravity to become a neutron star, rotating neutron stars emit radio signals called pulsars.
- If the star is very massive it may continue to collapse until all its mass is attracted to a single point, this is called a black hole because gravity is so strong that not even light can escape.
