Separate Q. What are the four main groups of objects that orbit the Sun?
- The Planets (8 in total)
- Dwarf Planets (e.g. Pluto)
- Natural satellites (e.g. our moon)
- Artificial Satellites
Separate Q. Describe how a star, like our Sun, is originally formed.
- A cloud of dust and gas (nebula) is pulled together by gravitational attraction.
- Temperature increases as the star gets denser and the particle collisions are more frequent.
- When the temperature is high enough, nuclear fusion of hydrogen begins to form helium nuclei.
- This nuclear fusion give out large amounts of energy and a star is born.
Separate Q. What would be the main stages of a life cycle of a star of similar size to our Sun?
- Cloud of gas and dust (nebula)
- Protostar
- Main sequence star
- Red Giant
- White Dwarf
- Black Dwarf
Separate Q. How do we know that Earth was formed after a supernova?
Only a supernova produces elements heavier than iron.
On Earth, there are elements heavier than iron.
Separate Q. What galaxy does our Solar System belong to?
The Milky Way
Separate Q. Describe how a main sequence star remains stable.
- The outward pressure caused by nuclear fusion is balanced by the force of gravity pulling inwards.
- An equilibrium is reached and the star remains stable for billions of years.
Separate Q. What would be the main stages of a life cycle of a star much bigger than our Sun?
- Cloud of gas and dust (nebula)
- Protostar
- Main sequence star
- Red Super Giant
- Supernova
- Neutron star or black hole
Separate Q. What process produces elements heavier than iron?
Supernova
Separate Q. What is the explosion of a massive star called?
Supernova
Separate Q. For an orbiting object, in which direction does gravity act?
Towards the centre of the object that is being orbited.
Separate Q. What process that takes place in stars produces all of the elements up to the size of iron?
Nuclear fusion
Separate Q. What evidence is there that the universe is expanding?
- Light from the most distant galaxies has an increased wavelength.
- The wavelength is shifted towards the red-end of the spectrum.
- This is called red-shift and it suggests the distant galaxies are moving away from us.
- Supernovae have been observed since 1998 and show distant galaxies are moving away at an accelerating rate.
Separate Higher Q. Explain how an object in orbit is accelerating without changing speed.
- Because the object is moving in a circle, it is constantly changing direction.
- This means it is constantly changing velocity.
- This also means it is constantly accelerating.
- Velocity and acceleration are both vectors that take into account both size and direction.
Separate Higher Q. What is the relationship between the speed of an object and the radius of its stable orbit?
The faster the object, the smaller the radius of its stable orbit.
Separate Q. Give two examples of things about the universe that are still poorly understood.
Dark matter – the name given to an unknown substance that scientists believe holds galaxies together but does not release EM radiation.
Dark energy – the name given to the energy thought to be responsible for the accelerated expansion of the universe.
Separate Q. What is the Big Bang Theory and how does red-shift provide evidence for it?
- The Big Bang Theory is the theory that the universe began from a small dense, hot region. Then it exploded and is continually expanding.
- Red-shift supports this as it shows that the universe is expanding in all directions. If you were to look back in the time, the universe must have begun at one single, small, dense point.
Separate Q. Name the force that keeps planets and satellites in orbit.
Gravity
Separate Q. Describe the transition from a main sequence star to a red giant, or red super giant.
- Hydrogen in the main sequence star begins to run out.
- The star swells.
- This becomes a red giant, or red super giant depending on the size of the main sequence star.
- It becomes red as the surface cools.
- Fusion of helium occurs and heavier elements (until elements up to the size of iron) are created.
Separate Q. Describe the transition from a red super giant to a neutron star or black hole.
- Red super giants undergo nuclear fusion creating elements as heavy as iron.
- They expand and contract.
- Eventually they explode (supernova) and create elements heavier than iron.
- The outer layers of dust and gas are ejected.
- This leaves a very dense core – called a neutron star.
- Very large stars can even result in the formation of a black hole.
Separate Q. What’s the relationship between the distance a galaxy is from us and the speed it’s travelling at?
The further away the galaxies, the faster they are moving.
Separate Q. Describe the orbit of planets going around our Sun.
The orbits are almost circular.
Separate Q. Describe the transition from a red giant through to a black dwarf.
- The outer layer of the red giant is ejected.
- This outer layer is dust and gas.
- A hot, solid, dense core is left. This is called a white dwarf.
- The White Dwarf cools and emits less and less energy until it becomes a black dwarf.
Separate Q. What is a black hole?
A highly dense point in space that not even light can escape from.
Separate Q. What evidence is there that the galaxies furthest away are travelling fastest?
Galaxies furthest away have a greater red-shift than nearer ones.
