What is a nebula?
A cloud of gas and dust
What is the lifecycle of a star for a star larger than the sun?
- Gravity in a nebula pulls the dust and gas together forming a protostar
- The star gets denser and temperature rises
- Hydrogen fusion begins in the stars core
- When the outward pressure of hydrogen fusion in the core is equal to the inward force of gravity the star becomes a main sequence star.
- Hydrogen nuclei begin to run out and larger elements begin to fuse (up to iron)
- The star expands to form a red supergiant
- This then leads to a supernova
- Smaller stars become neutron stars and massive stars become black holes
What is the lifecycle of a star that is a similar size to the sun?
- Gravity in a nebula pulls the dust and gas together forming a protostar
- The star gets denser and temperature rises
- Hydrogen fusion begins in the stars core
- When the outward pressure of hydrogen fusion in the core is equal to the inward force of gravity the star becomes a main sequence star.
- Hydrogen nuclei begin to run out and larger elements begin to fuse (up to iron)
- This expands to a red giant
- It collapses to form a white dwarf and cools forming a black dwarf.
What determines a stars life cycle?
Size of the star
What does fusion in stars produce?
All naturally occurring elements
What does a supernova do and produce?
Distributes elements throughout the universe, where they can form new stars and planets
Elements heavier than iron.
What is nuclear fusion?
When two light nuclei collide at high speed and join to create a larger heavier nucleus
Some mass is converted into energy and is released as radiation
Give examples of natural and artificial satellites
natural - moon
artificial - man made satellites
What causes circular orbits?
Gravitational force keeps planets in a circular orbit.
There is a constant speed, constantly changing direction and therefore a constantly changing velocity.
What happens when the speed of a stable object in orbit changes?
The radius of the orbit changes
The smaller the orbit the faster the object will travel
What is red shift?
An observed increase in the wavelength of light (shifts towards the red end of the spectrum)
Galaxy moves away from earth
What are the characteristics of a distant galaxy?
Moves away from earth faster
Has a greater red-shift
What evidence is there for the big bang theory?
Red-shift as it shows that the universe is expanding
What is the big bang theory?
All the matter in the universe occupied a dense and hot tiny region which exploded and started expanding
What did the observations of supernovae show in 1988?
Distant galaxies are receding at an increasing speed
What three things still aren’t fully understood?
- why distant galaxies are receding at increasing speeds
- dark matter
- dark energy
