Chapter 25 Vocab

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Across
  1. 4. law A law that states that the galaxies are retreating from the Milky Way at a speed that is proportional to their distance
  2. 8. giant A large, cool star of high luminosity (upper part of H-R)
  3. 12. A better unit to express stellar distance (9.5 trillion km)
  4. 13. a variable radio source of a small size that emits radio pulses in very regular periods
  5. 14. Star that falls into the main sequence category on the H-R diagram
  6. 18. An exploding star that increases in brightness many thousands of times
  7. 22. magnitude A star's brightness as it appears from Earth
Down
  1. 1. dwarf A star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size
  2. 2. Star groups
  3. 3. A group of stars close together
  4. 5. star Pairs of stars pulled together by gravity
  5. 6. a collapsing cloud of gas and dust destined to become a star
  6. 7. bang theory The theory that proposes that the universe originated as a single mass, which subsequently exploded
  7. 9. a cloud of gas and dust in space
  8. 10. giant A very large, very bright red giant star
  9. 11. hole A massive star that has collapsed to such a small volume that its gravity prevents the escape of everything including light
  10. 15. a star that explosively increases in brightness
  11. 16. star A star of extremely high density composed entirely of neutrons
  12. 17. magnitude How bright a star actually is
  13. 19. Slight shifting in apparent position due to orbital motion of Earth
  14. 20. A group of stars, dust, and gases held together by gravity
  15. 21. variable A star whose brightness varies periodically because it expands and contracts