P6

• Nebula


  a cloud of gas and dust
• What pulls the gas and dust in a nebula together, to form a protostar?

  the attraction of gravity
• As a protostar grows in size and attracts more particles from the surrounding nebula, what changes may take place within it?

  Nuclear fusion could initiate

  The temperature increases

  It becomes more dense
• Once nuclear fusion starts in a protostar, what does it become?

  a main sequence star
• The energy released from nuclear fusion creates an outward pressure that balances against the inward pressure from gravity.
• After the main sequence, what could a star become?

  A red giant

  A red super giant
• A main sequence star only fuses together hydrogen to make helium. 

  Then in red giants or red super giants, nuclear fusion can form heavier elements up to iron on the periodic table. 

  Elements heavier than iron are formed by supernovas. 
• For a red giant, what happens next in the star's lifecycle?

  It becomes a white dwarf and then a black dwarf
• For a red super giant, what happens next in the star's lifecycle?

  It explodes as a supernova
• What two alternative things might happen to a star after a supernova explosion

  Condense into a neutron star

  Collapse into a black hole
• The star cycle

  A) protostar

  B) main sequence star

  C) red giant

  D) super red giant

  E) white dwarf

  F) black dwarf

  G) supernova

  H) neutron star

  I) black hole

  
• Which side of the absorption spectra above has the longer wavelength?

  The red side on the left
• Red-shift is when light from distant galaxies show an absorption spectra pattern that has been shifted to the red side of the spectra
• Red-shift occurs because the light emitted by an object moving away from us will be stretched. The stretching causes the light's wavelength to increase. The faster an object moves away from us, the larger the red shift.
• What is the basic idea of the Big Bang theory?

  The Universe expanded from a single tiny point of high density and pressure