How old is the universe?
13.7 billion years.
Cosmology
The scientific study of the large scale properties of the universe.
Evidence for the Big Bang theory
- We are reasonably certain that the universe had a beginning
- Expanding universe - galaxies appear to be moving away from us at speeds proportional to their distance.
- Afterglow - cosmic microwave background radiation emitted within the universe now at a temperature of -270c
- Elements in the universe - the abundance of the light elements.
The Big Bang theory
The universe was through to have been concentrated into a single point of immense energy. An explosion within the first spilt seconds converted some of this energy to the simplest form of matter. Over time, the universe expanded and cooled and more complex matter formed.
Red shift
A shift to lower or redder frequencies and results from a star’s movement away from the Earth.
Blue shift
A shift to higher or bluer frequencies and is caused by a star’s movement towards the Earth.
What colour has the longest wavelength and lowest frequency?
Red.
What colour has the shortest wavelength and the highest frequency?
Violet.
Doppler effect
The change in the wavelength of radiation recovers from objects moving relative to us. As a star moves away from us, the wavelength becomes longer and the star appears red. As a star moves towards us, the wavelength shortens and the star appears blue.
Why are supernova events important?
Because it is within these violent explosions that heavy the heavy elements such as iron and lead are produced.
Life cycle of stars
All stars form from interstellar matter called nebulae, comprised mainly of hydrogen gas. This is compressed together by the force of gravity until the heat and pressure cause nuclear fusion to begin. The star is born.
How long is the life cycle of an average star?
10 billion years.
Our suns life cycle #1-3
- The sun evolves from a cloud gas. Gravity pulls it together. Pressure and temperature increase.
- A protostar. A ball of super hot gas. Contraction continues.
- Fusion starts in the core. The star joins the main sequence. Our sun will be on it for about 10 million years.
Our suns life cycle #4-5
- Hydrogen in the core begins to run out. Hydrogen in the outer layers starts to fuse causing expansion. The star becomes a red giant.
- The outer layers are ejected into space forming a planetary nebula. We are left with a very dense, hot white dwarf.
Outline two ways in which stars in the night sky can differ from each other.
- How bright they are
2. Their colour
What are some of the ideas people have put forward about how the universe was formed?
- Creationism - that God created heaven and Earth.
- Aboriginal Dreamtime ideas.
- Scientific theories - e.g the Big Bang theory.
Apparent magnitude
A measure of how bright a star appears from Earth and is the result of the stars distance from the Earth and how much light it emits.
Absolute magnitude
The amount of light a star emits.
What factors determine apparent and absolute magnitude?
- Size - larger stars tend to be brighter
- Surface temperature - brighter stars are white and tend to have a higher surface temperature. Less brighter stars are red and tend to have a lower surface temperature.
Nuclear fusion
A nuclear reaction in which multiple atoms combine under immense energy to create a star.
Solar mass
A standard unit of mass that is used to indicate the masses of other stars.
Is it likely that our sun may end its life in a supernova? Explain.
No, because it has a relatively low mass star. The sun will run out of hydrogen, explains up as a red giant, puff out its outer layers and settle down as a compact white dwarf.
Red Giants
Thermonuclear fusing of helium to iron
White dwarf
None
