Across
- 2. A variable radio source of small size that emits radio pulses in a very regular periods
- 6. A cloud of gas and/or dust in space
- 8. An exploding star that increases in brightness many thousands of times
- 9. A apparent group of stars originally named for mythical characters
- 11. A very large, very bright red giant star
- 12. A star whose brightness varies periodically because it expands and contracts
- 13. A star that falls into the main category on the H-R diagram
- 15. The brightness of a star when viewed from Earth
- 18. The theory that proposes that the universe originated as a single mass, which subsequently exploded
- 20. The slight shifting in the apparent position of a nearby star due to the orbital motion of Earth
Down
- 1. A system of galaxies containing from several to thousands of member galaxies
- 3. A star of extremely high density composed entirely of neutrons
- 4. A collapsing cloud of gas and dust destined to become a star
- 5. A law that states that the galaxies are retreating from the Milky Way at a speed that is proportional to their distance
- 7. The apparent brightness of a star if it were viewed from a distance of 32.6 light-years
- 10. A star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size
- 14. A star that explosively increases in brightness
- 16. The distance light travels in a year, about 9.5 trillion km
- 17. A group of stars, dust, and gas held together by gravity
- 18. A massive star that has collapsed to such a small volume that its gravity prevents the escape of anything; including light
- 19. A large, cool star of high luminosity