The Universe

3. A very large, bright, cool star that has run out of hydrogen at its core
5. Cloud of dust and gas occupying the space between stars; outer layers of a red giant after it runs out of fuel
8. The habitable zone around a star where the temperature is not too hot and not too cold
11. A region in space where gravity is so strong that nothing, not even light, can escape
12. A theoretical force responsible for accelerating the expansion of the universe
13. The distance that light travels in one year (about 10 trillion km)
15. A planet orbiting a star that is outside the solar system
17. The collapsed core of formerly massive stars
18. The most massive and luminous stars that burn much hotter and faster than smaller stars
20. The large explosion that scientists believe created the universe

1. A small, dense, dim star that has lost its outer layers and is at the end of its lifetime
2. A group of stars as seen from Earth that appear to form a familiar shape
4. Stars that convert hydrogen into helium at their cores; where 90% of stars in the sky are
6. An independent groups of stars that are held together by gravity
7. A group into which stars are classified based on their spectra/colour
9. Matter that does not emit light and is responsible for unidentified gravity in the universe
10. The explosion of a massive star
14. A change in the frequency of sound or light waves emitted from an object when its moves towards or away from an observer
16. The distance between Earth and the sun
19. A point at which an infinitely dense matter occupies an infinitely small space