XMAS SCIENCE CROSSWORD

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Across
  1. 4. The nuclear process that powers the "Star of Bethlehem" and all other stars (6)
  2. 5. The transition metal (atomic symbol Ag) used to make traditional shiny ornaments (6)
  3. 6. Reindeer are unique because both males and females grow these bony structures (7)
  4. 8. The phase change where water vapor turns directly into frost on a cold window (10)
Down
  1. 1. The pigment in evergreen needles that allows them to stay green all winter (11)
  2. 2. The "Northern Lights" often seen in the Arctic sky near the North Pole (6)
  3. 3. The universal "speed limit" Santa would need to approach to visit every house in one (10)night
  4. 7. A complex ice crystal that always forms with six-fold symmetry (9)