SPACE PHYSICS

• what do all stars begin as

  nebula (a cloud of dust and gas)
• what are nebulae pulled together by to form


  pulled together by gravity to form a protostar
• what does the gravitiational attraction cause to increase and what does this cause


  causes the density of a protostar to increase, causing more collisions between particles to occur, causing temp to rise enough for nuclear fusion to occur.
• what fuses in main sequence stars to form heluim


  hydrogen
• why are main sequence stars stable


  because of a balance between the energy released through nuclear fusion (which tries to expand the star) and gravitational attraction (which tries to compress it)
• what happens to stars as they begin to run out of hydrogen


  the begin to fuse heavier elements
• what is the fusion in stars responsible for


  producing all naturally occurring elements up to iron
• what does the life cycle of a star after the main sequence depend on

  mass
• what happens to stars that are the same size as the sun after the main sequence

  they become red giants
• what happens to red giants once they eventually eject their outer layer


  they become white dwarfs which cool to become black dwarfs
• what happens to stars bigger than the sun

  they turn into red super giants
• what happens when red super giants explode in supernova

  they form heavier elements than iron ejecting them into the universe
• what do supernova stars leave behind

  either a neutron star or for stars with a high enough mass a black hole
• what has produced all naturally occurring elements and distributed them through out the universe


  fusion in stars and supenovae
• what does our solar system contain

  one star (sun)

  8 planets

  dwarf planets

  natural satellites (moons)

  artificial satellites
• what is an orbit


  the path on which one object moves around another
• what do planets and dwarf planets orbit


  stars
• what do satellites orbit

  another more massive object
• where is our solar system located


  in the milky way
• what shape are orbits


  circular
• why do objects travel in orbit

  due to the force of gravity between two objects
• what direction does gravity act in an orbit and what does this cause


  acts towards the centre of the orbit, causing an acceleration which changes the velocity but not the speed of the orbiting object
• when is the gravitational force the strongest


  the closer you are to the object
• what does a faster orbital speed mean


  a smaller orbital radius for the object to be in a stable orbit
• what is the effect known as red shift


  light from distant galaxies has longer wavelengths than expected
• what does red shift


  all galaxies are moving away from us
• what is the relationship between the speed of distant and nearer galaxies

  distant galaxies are moving away faster
• what does galaxies moving away from us suggest

  the universe is expanding all galaxies are moving away from each other
• what do the observations of red shift support

  the big bang theory
• what does the big bang theory state


  that the universe was once confined to a very small area that was very hot and dense which exploded and has been expanding ever since
• what have the observations if distant supernova since 1998 shown

  that the expansion of the universe in accelerating
• what is the life cycle of a star determined by?

  the size of the star
• what is the general order of the life cycle of a star about the same size as the sun?

  nebula → protostar → main sequence star → red giant → white dwarf → black dwarf
• what is a nebula?

  a cloud of dust and gas
• how is a protostar formed?

  the force of gravity pulls the dust and gas together to form a protostar
• what are the fusion reactions in a protostar?

  hydrogen nuclei undergo nuclear fusion to form helium nuclei
• why does a main sequence star enter a long stable period?


  the expanding outward pressure caused by the nuclear fusion is balanced with the inward collapsing force of gravitational attraction
• how long is a star in the main sequence?


  several billion years
• why does a star swell into a red giant or super giant?

  the hydrogen begins to run out and the surface cools
• which fusion reactions occur in the red (super) giant?


  fusion of helium and other elements occur, elements heavier than iron created in the core