Chapter 28

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Across
  1. 2. a high-pressure form of hydrogen believed to exist inside Jupiter and Saturn that conducts electricity and contributes to strong magnetic fields.
  2. 6. a large planet composed mainly of water, ammonia, and methane ices.
  3. 11. a belt of asteroids located between the orbits of Mars and Jupiter.
  4. 14. an event that occurs when Earth passes through a stream of debris left by a comet, causing many meteors to appear in the sky.
  5. 15. an imaginary line through the center of a planet around which it rotates.
  6. 17. the four large planets farthest from the Sun: Jupiter, Saturn, Uranus, and Neptune.
  7. 19. a measure of how much an orbit deviates from a perfect circle.
  8. 21. a steep slope or cliff formed by faulting or erosion, sometimes observed on planetary surfaces.
  9. 23. a small rocky or metallic object moving through space.
  10. 25. the curved path an object follows as it revolves around another object in space.
  11. 27. a small icy body that orbits the Sun and forms a glowing coma and tail when heated near the Sun.
  12. 28. the apparent backward movement of a planet across the sky as Earth passes it in its orbit.
  13. 29. the force of attraction between objects due to their mass; it keeps planets in orbit around the Sun.
  14. 31. a small solid object formed from dust and gas in the early solar system that collided and combined with others to form planets.
  15. 32. a body that orbits the Sun and is nearly round but has not cleared its orbital path of other objects.
Down
  1. 1. the four rocky planets closest to the Sun: Mercury, Venus, Earth, and Mars.
  2. 3. an oval-shaped path followed by planets as they orbit the Sun.
  3. 4. the spinning of an object on its axis.
  4. 5. Belt a belt beyond Neptune containing icy objects and the source of many short-period comets.
  5. 7. a small rocky body that orbits the Sun, most commonly found between Mars and Jupiter.
  6. 8. the Sun and all objects that revolve around it due to gravity, including planets, moons, asteroids, and comets.
  7. 9. the movement of one object around another, such as a planet orbiting the Sun.
  8. 10. a natural satellite that orbits a planet.
  9. 12. a small, dense, rocky planet with a solid surface.
  10. 13. a meteoroid that survives passage through Earth’s atmosphere and strikes the ground.
  11. 16. a region of the solar system containing a large number of similar objects, such as the asteroid belt or Kuiper Belt.
  12. 18. the average distance between Earth and the Sun, about 150 million kilometers, used to measure distances within the solar system.
  13. 20. a very large planet composed mostly of hydrogen and helium, with no solid surface.
  14. 22. a large body that orbits a star, is nearly round due to gravity, and has cleared its orbital path of other objects.
  15. 24. a distant spherical zone surrounding the solar system that is thought to be the source of long-period comets.
  16. 26. a region of a planet or the solar system that has distinct characteristics, such as temperature or composition.
  17. 30. the streak of light produced when a meteoroid burns up in Earth’s atmosphere.