P8 - Space physics

• What is the life cycle of a star that is about the same size as sun?

  • nebula

  • protostar

  • main sequence star

  • red giant

  • white dwarf

  • black dwarf
• What is the life cycle of a star that is much bigger than size of sun?

  • nebula

  • protostar

  • main sequence star

  • red super giant

  • supernova

  • neutron star or black hole
• What is a nebula?


  cloud of dust and gas
• How is a protostar made?


  force of gravity pulls the dust and gas together
• What happens between a protostar and main sequence star?

  temperature raises as star gets denser and more particles collide with each other, when temperature gets high enough, hydrogen nuclei undergo fusion to form heluim nuclei which gives out huge amounts of energy which keeps the core of star hot
• What is a main sequence star?

  a star that enters a long stable period where the outward pressure caused by the nuclear fusion that tries to expand the star balances force of gravity pulling everything inwards
• How is a red giant or red super giant made?

  hydrogen runs out so star swells into red giant (smaller star) or red super giant, becomes red on surface as it cools and fusion of helium occurs, heavier elements are made in star core
• How is a supernova made?

  start to glow brightly as they undergo fusion, expanding and contracting several times forming elements like iron in nuclear reactions, explode in supernova producing and releasing elements heavier than iron to form new planets and stars
• How are neutron stars made?

  exploding supernova throw outer layers of dust and gas leaving very dense core
• How are black hole made?

  if star is massive enough, becomes a black hole, so dense not even light can escape
• How are white dwarfs made?

  small-to-medium-sized star becomes unstable and ejects outer layer of dust and gas, leaving behind a hot dense core
• How is a black dwarf made?

  white dwarf cools down, emitting less energy
• What is a satellite?


  an object which orbits a second bigger object
• Orbits:

  • object travelling in circle means constantly changing direction, meaning constantly accelerating - constant change in velocity but not speed

  • acceleration requires a force directing towards centre of circle

  • force causes object to fall towards orbit as its moving it changes direction

  • objects keeps accelerating towards object but constant velocity (at right angle to acceleration) keeps it travelling in circle

  • force used is gravitational force (gravity)
• Size of orbit:

  • closer you get to star or planet, stronger the gravitational force

  • stronger the force, the faster the orbiting object needs to travel to remain in orbit

  • in stable orbit if speed of object changes, so does the radius of orbit, faster moving objects orbit small radius
• What is red-shift?


  increases in wavelength so it shifts towards red end of spectrum