Stars

4. This is the only form of electromagnetic waves which we can see.
6. After gravity pulls the gas and dust in a nebula together, this is formed.
8. A group of stars.
11. This distance from the sun to the earth.
13. This may form at the end of a large sized star's life. Not even light can escape these.
14. This is measure of distance used in space. It is defined as the distance light travels in a year.
16. These electromagnetic waves have the smallest wavelength.
17. There are approximately 300 billion of these in our galaxy.
18. This gas is formed when two hydrogen atoms fuse together.
19. This type of spectra displays the frequencies of light that a hot gas emits.
21. The number of full cycles a wave completes in one unit of time.

1. Nuclear ____________ reactions occur in stars. These reactions produce the heat and light in stars.
2. These forms of waves include microwaves, infrared radiation and ultraviolet radiation.
3. This is the final stage of a low or medium sized star's life.
5. Stars begin their lives using up this gas.
7. These electromagnetic waves have the longest wavelength.
9. This is the most widely accepted theory in the scientific community explaining the creation of the universe.
10. The length between two consecutive peaks of a wave.
11. This type of spectra displays the frequencies of light that pass through a cold gas without being absorbed by it.
12. A large cloud of gas and dust. All stars start off as this.
15. This is used as evidence for the big bang theory as it shows that the universe is expanding.
20. This is the name of our galaxy.