Lifecycle of a Star

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Across
  1. 4. The joining together of hydrogen nuclei to form Helium (6)
  2. 7. a sun-sized star after main sequence, outer layers swelling and cooling (3,5)
  3. 9. a medium star exploded leaving a small hot dense remaining center (5,5)
  4. 12. the limit of pressure of a white dwarf to collapse (8,10)
  5. 14. The emissions given off by any object with thermal energy in it (9,10)
  6. 15. An extremely massive star
  7. 16. Interstellar cloud of dust and gas (6)
  8. 17. The force responsible for the gathering of a protostar (7)
  9. 18. The source of a star's radiation energy (6)
Down
  1. 1. The coloured nebulous remains around a white dwarf (9,6)
  2. 2. Colour of the hottest stars in the universe (4)
  3. 3. A large star collapsed into a singularity (5,4)
  4. 5. A large star collapsed to about 20km diameter (7,4)
  5. 6. The stable Hydrogen-burning phase of a star's life (4,8)
  6. 8. A small star(5)
  7. 10. The fuel source of a Red Giant, after Hydrogen fusion ends (6)
  8. 11. The metal element at the center of large mature stars (4)
  9. 13. The least energetic of the ionizing Electromagnetic waves (11)
  10. 15. Extremely bright explosion of a star (9)