P7.5
- Created by: amy_mair
- Created on: 23-06-16 22:18
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- P7.5
- Star Spectra
- Frequencys
- Continuous spectra contain all possible frequencies
- 1. All hot objects like stars emit radiation
- 2. Hot objects always emit more of one frequency than the other
- 3. The peak frequency emitted by an object depends on its temperature
- 4. The luminosity or brightness also depends on temperature- hotter things glow more
- 5. For example we can tell how hot a star is by looking at its colour
- Blue- Hot
- Red- Cooler
- Line Spectra
- Electrons moving between energy levels
- 1. Atoms only contain electrons which move around a tiny positive nucleus
- 2. Electrons can only be in certain energy levels around the nucleus
- 3. Electrons move between energy levels if they gain or lose energy
- 4. Electrons can gain energy to be removed from the atom
- What are stars made of
- 1. Energy levels in atoms are different for each element
- The photosphere of a star emits a continuous spectrum of radiation
- 3. By looking at the position of these lines in the stars spectrom you can work out the chemical elements are present in the stars atmosphere
- Frequencys
- Stars
- Beginning
- They begin as dust and gas
- 1. Gravity causes the denser regions of the cloud to contract very slowly into clumps (they collapse under the force of gravity
- 3. As pressure increases temperature increases yet as volume decreases pressure increases
- 2. When these clumps get dense enough, the cloud break up into photostars
- 5. Eventually the temperature increases and the hydrogen nuclei start to fuse together to form helium
- 6. This releases an enormus amount of energy and creates outward pressure
- 7. It now has reached the main sequence stage
- The core
- A star is made up of a core surrounded by different layers
- The core- most of the fusion takes place in the centre. The presure from the weight of the rest of the star makes the core hotter and denser
- Surface: The outer region of the star, from where energy is radiated into space.
- Energy is released from fusion in the core is transported by photons of radiation and convection currents to the surface of the star
- Main sequence stars
- 1. Contains hydrogen. It stops being main sequence when it runs out of hydrogen in the core
- 2. It then swells and becomes a red giant
- Photosphere cools down
- Beginning
- Life Cycle of the stars
- Story of stars
- 1. All stars change when there is no longer enough hydrogen in the core for fusion to carry on
- 2. The core is compressed by the surrounding matter of the star and shrinks
- 3. Once there is not enough helium it becomes unstable
- 4. A red giant does not have enough mass to compress the core so no more nuclear fussion occurs. It forms white dwarfs
- 5. Red super giants do have enough mass to increase the pressure of the core enough to fuse larger nuclei
- 6. Super red giants can not fuse iron but when it super novas it creates elements bigger than iron
- 7. The core collapes to form a neutron star
- Story of stars
- Telescopes
- Types
- Local and remote
- 1. Instead of an astronmer having to always be there, they now just program the telescope to track the objects in the sky
- 2. Computer controls can also be used as they can be positioned more precisely
- 3. They like putting them in deserts as they dont have to spend time or money travelling
- 4. Astronomers need many telescopes pointing in the same direction
- 5. They need a network of telescopes every night
- Computers are also used to record and process data
- Types
- Star Spectra
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