Across
- 3. A cloud of gas and dust in outer space
- 5. A celestial object consisting of a nucleus of ice and dust
- 7. A group of stars forming imaginary pictures
- 9. A small body of matter from outer space that enters the earth's atmosphere
- 11. A unit of astronomical distance equivalent to the distance that light travels in one year
- 12. Disk-shaped region of minor planets outside the orbit of Neptune
- 13. A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
- 15. Occurs after low or medium density star phase
- 18. The "brain" of the comet
- 19. Former Meteor
- 20. A massive and extremely remote celestial object, emitting exceptionally large amounts of energy
Down
- 1. A diffuse cloud of gas and dust surrounding the nucleus of a comet
- 2. Occurs after high-density star phase
- 4. Belt of asteroids
- 6. A spherical cloud of small rocky and icy bodies postulated to orbit the sun beyond the orbit of Pluto
- 8. Contains neutrons
- 10. A contracting mass of gas that represents an early stage in the formation of a star
- 14. Region of space from which nothing, not even light, can escape
- 16. An explosion in space
- 17. A small rocky body orbiting the sun