Astronomy

2. Nodding motion of the earth's precession that causes the seasons
4. A collection of gas, dust, and billions of stars and their solar systems
8. The slow & continuous pointing of Earth's axis in different directions over a 26,000 year cycle
10. An object's orbital motion around another object
11. When the wavelength of something is stretched so it appears stretched toward the red end of the spectrum

1. The reaction in which two atoms of hydrogen fuse to form a helium nucleus - This process powers the Sun!
2. A cloud of dust and gas between stars that has new stars
3. The center of mass between two orbiting objects where all the mass and gravity are equally distributed
5. An object's spinning motion about its own axis
6. The process of two smaller atoms forming from a collision
7. All of space, matter, and energy
9. The elliptical orbit that a planet travels in