space physics

• What determines the end of a star's life cycle?

  The star's mass
• What are the main stages in the life cycle of a star with the same/smaller mass of the Sun?

  1. Nebula
  2. Protostar
  3. Main Sequence Star
  4. Red Giant
  5. White Dwarf
  6. Black Dwarf
• What is a nebula?

  A cloud of dust and gas particles from the start of the Universe or remnants of planet and star formation
• What happens during the formation of a protostar?

  The particles are drawn together under their own gravity, leading to thermonuclear fusion reactions
• What is a main sequence star?

  A star that fuses small hydrogen and helium atoms into larger atoms like carbon and iron
• What elements were present in the early Universe?

  Only hydrogen
• What balances the forces in a star to keep it stable?

  The force of gravity attracting particles towards the center and the pressure from fusion pushing them out
• What happens to a star when almost all of its hydrogen is used?

  It expands into a red giant
• What is a white dwarf?

  A hot, dense mass that remains after most of the matter from a red giant is distributed to the surroundings
• What is a super red giant?

  A larger version of a red giant with a much denser core
• What occurs during a supernova explosion?

  The star rapidly collapses, creating intense heat and pressure that leads to further fusion
• What is a neutron star?

  A very small, extremely dense, rapidly-spinning star that may remain after a supernova
• How is a black hole formed?

  From the remnants of the heaviest stars that have a strong gravitational pull
• What is required for circular motion to occur?

  A centripetal force
• What are the most likely forces to act as a centripetal force?

  Gravity, tension, friction, and reaction
• What is centripetal acceleration?

  The acceleration that acts towards the centre of the circular path due to unbalanced centripetal force
• How does centripetal force relate to mass, velocity, and radius of orbit?

  Centripetal force is proportional to mass and velocity squared, and inversely proportional to the radius of orbit
• What is the formula for centripetal force?

  force = mass x velocity squared / radius
• What is a satellite?

  An object that has an orbit
• How does gravity affect satellites?

  The pull of gravity between two objects acts as a centripetal force
• What are the two types of satellite orbits?

  1. Geostationary: Always fixed above the Equator, orbits once every 24 hours.
  2. Circumpolar: Passes the North and South Poles, orbits once every 1.5 to 3 hours.
• What are the differences between geostationary and circumpolar satellites?

  Geostationary:

  • orbits once every 24hrs
  • orbits with Earth's rotation - always above the same point on the Earth
  • orbit radius is around 6x the Earth's radius
  • only enough room in space for around 400 geostationary satellites.

  Circumpolar:

  • orbits once every 1.5 to 3hrs
  • orbit is not above the same position - "scans" the surface of the Earth regularly
  • orbits a few hundred kilometres above Earth
  • can be more polar orbiting satellites - could have five in view at any one time
• What are the main stages in the life cycle of a star with the larger mass than The Sun?

  1. Nebula
  2. Protostar
  3. Main Sequence Star
  4. Super Red Giant
  5. Supernova
  6. Neutron Star (less heavier stars)
  7. Black Hole (heavier stars)
• What are the uses of satellites?

  Geostationary:

  • Communication - TV, radio, telephone
  • GPS and satellite navigation

  Circumpolar:

  • Weather forecasting - detailed
  • Land surveys - studies of land usage, mapping etc.
• What is the most commonly believed explanation for the origin of the Universe?

  The Big Bang Theory
• Who made the prediction about the Universe starting from a central point?

  Edwin Hubble
• What does the movement of stars and galaxies away from us suggest about the Universe?

  It suggests that the Universe must have started from a giant outpouring of matter from one central point.
• What happens to matter from the Big Bang as it cools?

  Stars, galaxies, and planets are able to form.
• What is the future possibility for the Universe if there is enough matter?

  The Universe could collapse in 'The Big Crunch'.
• How long until 'The Big Crunch' could potentially happen?

  It will not happen for billions of years.
• What are the two types of Universes mentioned?

  • Low Mass Universe
  • High Mass Universe
• What does the Doppler Effect apply to?

  It applies to all types of waves, both transverse and longitudinal.
• How did Hubble use the Doppler Effect in his observations?

  He observed the Doppler Effect in light from galaxies to conclude that the Universe is expanding.
• What does the Doppler Effect show about light moving away from us?

  The wavelength increases as the light moves away.
• What did Hubble observe when he attached a diffraction grating to his telescope?

  An absorption spectrum was absorbed.
• What does the absorption spectrum show?

  It shows a continuous band of colors interrupted by black (Fraunhofer) lines at certain positions.
• How can measuring the wavelengths of the Fraunhofer lines be useful?

  It can be used to characterize each element and determine the star's composition.
• What did Hubble observe about the spectra of many galaxies over time?

  Many galaxies displayed a red shift.
• What does a red shift in spectral lines suggest?

  It suggests that the galaxy is getting further away from us.
• What does a blue shift in spectral lines indicate?

  It indicates that the galaxy is getting closer to us.