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