physics - astrophysics

• difference between the orbits of planets and comets

  orbits of planets are roughly circular

  orbits of comets are elliptical
• force that causes one object to orbit around another

  gravity
• solar system

  The sun and the planets, dwarf planets and asteroids that orbit the Sun
• planet

  spherical body that orbits a star in roughly circular orbit, and contains majority of mass in the orbit
• life cycle of a star larger than the Sun

  • nebula
  • protostar
  • main sequence
  • red supergiant
  • supernova
  • black hole or neutron star
• what happens to the pitch of sound when the source moves towards the observer

  it is higher as the waves are compressed
• apparent magnitude of a star

  how bright it appears to be
• relationship between gravitational field strength and mass of the planet

  greater the mass, greater the gfs

  directly proportional
• two factors that affect how bright a star appears to be

  actual brightness and distance
• big bang theory

  all matter in the universe started in one hot dense place before an explosion and expansion
• equation linking orbital speed, time period, and orbital radius

  orbital speed= 2pi x orbital radius / time period
• magnitude of dimmest stars

  largest positive numbers
• orbital period

  time taken for one orbit to be completed
• what happens to pitch of sound when source moves away from an observer

  it decreases as waves are stretched
• star classes (hottest to coolest)

  O(oh)

  B(be)

  A(a)

  F(fine)

  G(guy)

  K(kiss)

  M(me)
• moon

  natural satellite that orbits a planet
• 2 sources of evidence for Big Bang Theory

  Red Shift, Universe is expanding

  Cosmic Microwave Background Radiation (leftover radiation from the Big Bang Theory)
• range of temperatures for star (approx)

  3000K to over 33000K
• red shift

  increased wavelength observed from a star or galaxy moving away
• absolute magnitude

  brightness of a star observed at a standard distance of 10 parsecs (32.6 light years away)
• magnitude of brightest stars

  largest negative numbers
• colour of hottest stars

  blue
• source of CBMR

  energy released in the Big Bang (red shifted)
• luminosity

  actual brightness of star, measure of energy emitted every second
• change in wavelength= velocity of galaxy/ speed of light
• y axis of a Hertzsprung-Russel diagram

  increasing luminosity
• galaxy

  group of billions of stars
• doppler effect

  apparent change in frequency of a wave due to the source moving relative to the observer
• life cycle of a star the same size as the Sun

  nebula, protostar, main sequence, red giant, white dwarf
• x axis of Hertzsprung- Russel diagram

  decreasing temperature
• colour of coolest stars

  red