astronomy final crossword

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Across
  1. 1. the way electromagnetic radiation travels through space
  2. 3. The part of the Sun that emits the radiation we see
  3. 5. the backwards motion of planets
  4. 7. the third largest object in the sky
  5. 9. the thin layer of gas on the outer edge of a planet
  6. 11. the most geologically active object in the solar system
  7. 12. A microorganism, especially an Archaean, that lives in conditions of extreme temperature, acidity, alkalinity, or chemical concentration
  8. 13. The dense, opaque region at the center is called a
  9. 15. Relating to the origin and development of the universe
  10. 16. a type of evolution we see in the sky and on planets
  11. 18. A celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves
Down
  1. 2. A pattern of lines or rays radiating from a central object or source of light
  2. 3. A star with a parallax of 1 arc second is 1
  3. 4. the inner planets they are small, dense, and rocky
  4. 6. the study of space and celestial objects
  5. 8. The central and most important part of an object, movement, or group forming the basis for its activity and growth
  6. 10. A star showing a sudden large increase in brightness and the slowly returning to it original state over a few months
  7. 14. a "light bucket" used to view space
  8. 17. a gargantuan collection of stellar and interstellar matter—stars, gas, dust, neutron stars, black holes