HideShow resource information
  • Created by: amy_mair
  • Created on: 23-06-16 22:18
View mindmap
  • 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
    • 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
    • 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
    • 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


No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Astronomy resources »