Vocabulary
gravity, supernova, nebula, protostar, friction, static electricity, asteroid belt, black hole, phases, moon, satellite, solar system, waxing, waning, crescent, gibbous, quarter, cycle, orbit, eclipse, lunar eclipse, solar eclipse, solar system, phases of the moon, waxing, waning, gibbous, crescent, irregular, elliptical, spiral, gravity, galaxy, Milky Way, solar system, Hubble Telescope, barred spiral, reflecting, refracting, optical telescope, open cluster, globular telescope, O.B. stars, differential rotation, light year, orbit, x-ray telescope, radio telescope, solar system, gravity, revolution, equator, southern hemisphere, northern hemisphere, solstice, equinox, eclipse, umbra, penumbra,, solar system, planets, asteroids, gravity, atmosphere, celestial body, inertia, comet, meteoroid, meteor, orbit, inner planet, natural satellite, terrestrial planets, outer planet, retrograde, radio waves, dwarf planet, comets, asteroids, gravity, velocity, orbital, lander, rover, telescope, ocular, finderscope, tripod, solar system, asteroid belt, gravity, solar system, planets, inner planet, gas giants, asteroids, comets, sun, hydrogen, helium