1. 2. planet a celestial body resembling a small planet but lacking certain technical criteria that are required for it to be classed as such
  2. 5. a unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun
  3. 7. Allen belt each of two regions of intense radiation partly surrounding the earth at heights of several thousand kilometers
  4. 10. the stabilizing and guiding unit of a model rocket, an aerodynamic surface projecting from the rocket body for the purpose of giving the rocket directional stability
  5. 12. the path of a celestial body in its revolution about another
  6. 14. an optical instrument designed to make distant objects appear nearer, containing an arrangement of lenses, or of curved mirrors and lenses, by which rays of light are collected and focused and the resulting image magnified
  7. 15. any celestial body orbiting around a planet or star
  8. 17. a compartment for the pilot and sometimes also the crew in an aircraft or spacecraft
  9. 18. movement, or a tendency to move, toward a center of attractive force, as in the falling of bodies to the earth
  10. 19. lacking a crew
  11. 20. cargo of rocket
  1. 1. a space entirely devoid of matter
  2. 3. a celestial body moving in an elliptical orbit around a star
  3. 4. a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure
  4. 6. a small celestial body composed of rock and metal
  5. 8. recovery rocket recovery system in which the engine's ejection charge causes it to convert into a glider which creates lift as it flies through the air
  6. 9. a jet engine containing its own propellant and driven by reaction propulsion
  7. 11. each of a series of Soviet artificial satellites, the first of which was the first satellite to be placed in orbit
  8. 13. a person trained to travel in space
  9. 16. the federal agency that built and operated the space shuttles from 1981 through 2012