Astrophysics

• Solar System


  A collection of planets that orbit a star
• Universe


  A large collection of billions of galaxies
• What is the order of the planets?


  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• Galaxy


  A system of a hundred billion stars and solar systems
• What is the relationship between orbital period and radius from the sun to the planets?


  The orbital period is directly proportional to the radius
• Inner Four Planets Traits


  Have shorter orbits, nearly all the same size
• Outer Four Planets Traits


  Much larger in size
• Difference between a moon and a planet


  Moons orbit planets, not stars
• Orbital Period


  The time taken to complete one orbit
• What is a comet made of?


  Dust, rock and ice
• What is a comet's orbit like?


  An elliptical (oval) shape
• What is the relationship between gravity and mass?


  The larger the planet's mass, the larger the gravitational field strength (directly proportional)
• Weight Equation


  weight = mass x gravitational field strength
• What is the difference between planets and dwarf planets?


  Dwarf planets are smaller so have a smaller gravitational force. This means they fail to clear the path of its orbit
• Asteroid


  A predominantly rocky, non-spherical object in space
• Meteorite


  A rocky object that burns up when entering the atmosphere
• Comet


  An icy and rocky object with an eccentric orbit
• Why do planets nearer the star take less time to orbit it?


  The star will have a stronger pull of gravity on planets closer to it so the planet's orbit (circumference) will be less
• Orbital Speed Equation


  orbital speed = 2 x pi x orbital radius / time period
• How to answer a statement evaluation question?


  How do you agree, how do you disagree, back up with data
• Star Phases for a star like the Sun


  Nebula, main sequence, red giant, white dwarf, black dwarf
• Nebula


  The Nebula is a cloud of gas that collapses under its own gravity and heats up
• Main Sequence


  Hydrogen comes together under gravity until it is hot enough to start fusion. Hydrogen fuses into Helium. Gravity and fusion are now in equillibrium.
• Red Giant


  The star runs out of hydrogen so the core contracts and the outer layers expand and cool.
• White Dwarf


  Once the outer layers are fully gone, just the core is left over.
• Black Dwarf


  The core cools down to make (in theory) a black dwarf
• Main Sequence to Red Super Giant


  The star runs out of hydrogen so the core contracts and the outer layers expand. It then tries to fuses other elements
• Red Super Giant to Super Nova


  The star tries to fuse other elements until it reaches Iron, which is not possible so the core collapses and explodes
• Super Nova to Neutron Star


  A really dense and hot core is all that remains
• Super Nova to Black Hole


  The biggest cores become black holes. These are so dense, light from away gets sucked in (it is actually really small in a physical sense)
• Luminosity


  The brightness of the star compared to the sun
• Absolute Magnitude


  The brightness of the star if considered at a 'set' distance
• Spectral Class Types for Stars


  OBAFGKM
• Where are blue stars on a Hertzsprung-Russel diagram?


  The left (30000-20000)
• Where are red stars on a Hertzsprung-Russel diagram?


  The right (4000-3000)
• Where are main sequence stars on a Hertzprung-Russel diagram?


  The middle going down

  
• Where are giants and supergiants on a Hertzsprung-Russel diagram?


  The top
• Doppler Effect


  An apparent change of frequency or wavelength caused by relative motion between the source and observer
• Relative Speed of a Galaxy Equation


  change in wavelength / original wavelength

  =

  velocity of galaxy / speed of light
• Spectral Lines


  Gaps where light should have been, the elements