Topic 5 - Stars and Planets

• In which galaxy is our solar system?

  The Milky Way galaxy.
• How many planets make up our solar system?

  Eight (plus the dwarf planets).
• What do the planets in our solar system orbit around and what type of body is it?

  • The planets orbit around the sun
  • The sun is a star
• What type of force pulled together the cloud of dust and gas to form the Sun?

  Gravitational force of attraction.
• What word is used to describe a cloud of dust and gas?

  A nebula.
• What type of reactions take place at the start of a star's life cycle as dust and gas is drawn together?

  Fusion reactions.
• What factor determines the type of life cycle a star undergoes?

  The size (and therefore mass) of the star.
• Which two phases do all stars of the same or greater size than the sun undergo?

  1. Protostar phase
  2. Main sequence phase
• What do stars like the sun become at the end of their life-cycle?

  A black dwarf.
• What two things can stars much bigger than the sun become at the end of their life cycle?

  1. Neutron star
  2. Black hole
• Which two phases do stars like the sun experience between being a main sequence star and a black dwarf?

  1. Red giant
  2. White dwarf
• What two phases do stars of greater size than the sun go through between being a main sequence star and a neutron star/black hole?

  1. Red supergiant
  2. Supernova
• What is produced during the fusion processes in a star?

  Atoms of all of the naturally occurring elements.
• What condition is required for fusion reactions to occur in a star?

  Very high temperatures and pressures.
• Where are elements heavier than iron produced?

  In a supernova.
• What type of nuclei fuse together to form heavier elements in a star?

  Hydrogen nuclei fuse to form heavier elements.
• How are elements distributed throughout the universe?

  Through the explosion of a massive star (supernova).
• What allows planets and satellites to maintain circular orbits?

  • Gravity provides the gravitational force that acts as the object's centripetal force.
  • The presence of a centripetal force allows for the object to maintain its circular orbit.
• What type of satellite can a planet's moon be described as?

  A natural satellite.
• Give two examples of artificial satellites.

  1. TV satellites
  2. Satellites used for satellite imaging
• What type of planet is Pluto classed as?

  A dwarf planet.
• What is the name given to the natural satellites that orbit planets?

  Moons.
• Give a basic description of a comet.

  A high speed ball of ice and rock which, as it melts, leaves a trail of dust and gas behind it.
• What term is given to the four outer planets of our solar system?

  Gas giants.
• What is a light year a unit of?

  • Distance
  • Used for the distances between the Earth and stars and other galaxies
• What unit of measurement is used to measure distances between the sun and planets?

  The Astronomical Unit (AU).
• What colour stars are the hottest? Blue or red?

  • Blue stars are the hottest stars
  • Red stars are the coolest stars
• What does a Hertzsprung-Russell diagram show?

  The luminosity of stars against their temperature.