Topic 8- Space Physics

• What are the stages of a star?

  Cloud of dust and gas → protostar → main sequence star → red giant / super red giant
• What are the stages of a star after a red giant?

  White dwarf → black dwarf
• What are the stages of a star after a red super giant?

  Supernova → neutron star or black hole
• How is a protostar created?

  -force of gravity pulls the dust and gas together to form a protostar

  -temperature rises as star gets denser and more particles collide iwth each other

  -when temperature is high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei

  -releases huge amounts of energy which keeps the core of the star hot
• How is a main sequence star formed?


  -star enters a long stable period

  -outward pressure (caused by nuclear fusion wanting to expand) balances the force of gravity

  -lasts for several billion years
• How is a red giant/ super giant formed?


  -hydrogen begins to run out

  -star swells into a red giant or red super giant is its larger

  -becomes red because the surface cools

  -fusion of helium occurs

  -heavier elements are created (up to iron) in the core of the star
• What is a red giant?

  Stars the about the same size as the sun
• What is a red super giant?

  Stars much larger than the sun
• How is a white dwarf formed?


  -star becomes unstable and ejects its outer layer of dust and gas

  -leaves a hot, dense solid core
• How is a black dwarf formed?


  -white dwarf cools down and emits less and less energy

  -when it no longer emits a significant amount it's called a black dwarf
• How is a supernova formed?

  -starts to glow brightly again as they undergo more fusion and expand and contract several times

  -forms heavy elements like iron in various nuclear reactions

  -then they'll explode in a supernova

  -forms elements heavier than iron which are released into atmosphere to form planets and stars
• How is a neutron star formed?

  -exploding supernova releases the outer layers of dust and gas into space

  -leaves a very dense core called a neutron star
• How is a black hole formed?

  -if the star is large enough it will form a black hole

  -it's a very dense point in space that light cannot escape from
• What do planets do?

  Orbit a star, have to have enough gravity to have pulled in any nearby objects apart from their natural satellites
• What are dwarf planets?


  Planet-like objects that orbit stars, don't meet all the rules to be classed as a planet (pluto)
• What are moons?


  Natural satellites that orbit planets
• What are artificial satellites?


  Satellites that humans are built, generally orbit earth
• What is our solar system apart of?

  The milky way galaxy (massive collection of billions of stars that are held together by gravity)
• What is an object doing if it's constantly moving in a circle?

  Changing direction which means it's constantly accelerating and changing velocity
• What does the size of an orbit depend on?

  An objects speed (stronger gravitational force = faster speed)
• What is red-shift?


  When we look at light from most distant galaxies, the wavelength has increased- the wavelengths are all longer than they should be which means they are towards the red end of the spectrum. This suggests that light is moving away from us (galaxies are moving away)
• How was the Big Bang Theory discovered?

  As the galaxies are moving away from each other at great speed, something must've produced that movement- which is the explosion
• What is dark matter?


  The name given to an unknown substance that holds galaxies together but doesn't emit any electromagnetic radiation
• What do scientist think the universe is mostly made up of?

  Dark matter and dark energy