Star Crossword Puzzle. (plus a few extra things)

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Across
  1. 3. The planet that's mostly water.
  2. 4. it happens after the red giant stage
  3. 6. The Last stage of a star's life cycle
  4. 7. The brightest star in the sky
  5. 8. It's the main stage of a star's life
Down
  1. 1. The second-to last star's life cycle, typically the smallest form
  2. 2. The beginning of a star's life
  3. 5. The Biggest Star in the galaxy and/or universe
  4. 7. it's what we're in right now (it has multiple planets)