1. 5. the time it takes for an object to orbit another object; Earth’s revolution around the Sun is 365.24 days
  2. 7. a celestial body made of hot gases, mainly hydrogen and some helium
  3. 9. a huge collection of stars, planets, gas, and dust that is held together by gravity
  4. 10. an object in space that ranges in size from a tiny speck, like a grain of sand, to 500 km wide; most asteroids originate in the asteroid belt between Mars and Jupiter
  5. 11. an object composed of rocky material, ice, and gas; comes from the Kuiper Belt or Oort Cloud
  6. 12. the turning of an object around an imaginary axis running through it; Earth’s rotation around its axis is 24 h
  7. 14. a piece of rock moving through space
  8. 16. a small, dim, hot star
  9. 17. a star’s total energy output per second; its power in joules per second
  10. 19. a meteoroid that is large enough to pass through Earth’s atmosphere and reach the ground, without being totally burned up
  1. 1. a scientist who studies astronomy
  2. 2. a massive explosion in which the entire outer portion of a star is blown off
  3. 3. the monthly progression of changes in the appearance of the Moon that result from different portions of the Moon’s sunlit side being visible from Earth
  4. 4. an artificial (human-made) object or vehicle that orbits Earth, the Moon, or other celestial bodies; also, a celestial body that orbits another body of larger size (for example, the Moon is Earth’s natural satellite)
  5. 6. the distance that light travels in one year, about 9.5 × 1012 km The 12 is supposed to be on the top right corner of 10
  6. 7. a group of planets that circle one or more stars
  7. 8. an object that orbits one or more stars (and is not a star itself), is spherical, and does not share its orbit with another object
  8. 13. the galaxy that includes the solar system; appears as a hazy white band in the night sky
  9. 15. a way of showing days, organized into a schedule of larger units of time such as weeks, months, seasons, or years; usually a table or a chart
  10. 18. a meteoroid that hits Earth’s atmosphere and burns up