THE UNIVERSE

4. the broad line that most stars fall on, on a H-R diagram
8. A collapsing cloud of gas that is to become a star
9. The result when waves produced by a moving source are either lengthened or shortened due to the motion of the source
10. A hot, dense star which is the remnant of a red giant
11. A massive explosion that occurs when a star larger than our sun, runs our of nuclear fuel
12. Mass of a unit volume of a material substance
13. A big group of stars drawn to each other by gravity
14. The study of the history and structure of the entire universe
15. Very high-frequency electromagnetic rays
17. A large star of low surface temperature and produced when the core of a sun-sized star runs out of hydrogen
18. The measure of the brightness of a star
19. A cloud of gas found in the empty space between stars
20. A device that splits light into spectrum in order to show its factor wavelengths

1. A collapsed star so giant that even light is unable to escape from its gravitational field
2. The remnant of a supernova, made up entirely of neutrons
3. The distance light travels in a year
4. The galaxy which contains our solar system
5. The classification system for stars based on their colour
6. The study of stars
7. The force in which attracts two things together
16. A measure of how bright the star will appear to an observer on Earth