Terms in this set (20)

  • asteroid
    a small, rocky object that orbits the sun
  • comet
    a small, rocky and icy object that orbits the Sun
  • astronomical unit
    The average distance between Earth and the sun, about 150 million kilometers
  • period of revolution
    the time it takes an object to travel once around the Sun
  • terrestrial planet
    Mercury, Venus, Earth, and Mars-the planets closest to the Sun that are made of rock and metallic minerals and have solid outer layers
  • greenhouse effect
    the natural process that occurs when certain gases in the atmosphere absorb and reradiate thermal energy from the Sun
  • galilean moons
    The four largest moons of Jupiter's 63 moons discovered by Galileo
  • meteroid
    a small rocky particle that moves through space
  • meteor
    a meteoroid that has entered Earth's atmosphere and produces a streak of light
  • meteorite
    a meteoroid that strikes a planet or a moon
  • impact crater
    a round depression formed on the surface of a planet, moon, or other space object by the impact of a meteorite
  • spectroscope
    An instrument that separates light into different wavelengths
  • light year
    the distance light travels in one year
  • apparent magnitude
    a measure of how bright an object appears from Earth
  • luminosity
    the true brightness of an object
  • galaxy
    A collection of stars, dust, and gas bound together by gravity
  • dark matter
    matter that emits no light at any wavelength
  • Big Bang Theory
    the universe began from one point billions of years ago and has been expanding ever since
  • Doppler Shift
    the shift to a different wavelength
  • period of rotation
    the time it takes an object to complete one rotation