Astronomy crossword puzzle

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Across
  1. 5. Famous for its ring system
  2. 6. The dense core left after a supernova of a high mass star
  3. 10. A rotating neutron star emitting beams of radiation
  4. 11. The farthest planet from the Sun
  5. 12. A burst of energy as a star starts fusing helium
  6. 15. A massive stars phase before a supernova
  7. 18. The only planet known to support life
  8. 19. Material spiraling into a black hole or neutron star
  9. 21. A phase where a star expands as it runs out of hydrogen
Down
  1. 1. The largest planet in the solar system
  2. 2. The birthplace of stars a cloud of gas and dust
  3. 3. A region of space where gravity is so strong that nothing escapes
  4. 4. The stable phase in a stars life where it fuses hydrogen
  5. 7. The boundary around a black hole where nothing can escape
  6. 8. A powerful explosion marking the death of a high mass star
  7. 9. The small dense remnant of a low mass star
  8. 10. A young star
  9. 13. A planet that rotates on its side
  10. 14. The process by which stars produce energy by fusing atoms
  11. 16. Known as Earths sister planet
  12. 17. The smallest planet and closest to the Sun
  13. 20. Known as the Red Planet