| A | B |
|---|
| astronomy | the study of objects in the Universe |
| solar system | the Sun and our nine planets |
| universe | EVERYTHING makes it up |
| Big Bang | scientific theory about the origin of the Universe |
| galaxies | large systems of millions and millions of stars held together by gravity |
| nebula | gigantic cloud of space dust and gases, birthplace of stars |
| nebular hypothesis | idea that our solar system formed from a nebula |
| geocentric model | idea that our solar system revolves around the Earth |
| heliocentric model | means that the Sun is the center of the solar system |
| Copernicus | Polish astronomer who wrote about the Heliocentric model |
| Galieo | Italian scientist who used the telescope to prove the Heliocentric model |
| Sir Isaac Newton | English scientist who defined gravity, gave us 3 laws of gravity, & Law of Universal Gravitation |
| scientific method | system for solving problems using hypothesis and experimentation |
| gravity | force that all objects exert on each other |
| irregular galaxies | have no real shape, many newer stars and lots of gases and dust |
| spiral galaxies | shaped like pinwheels, has a central bulge with older red stars, spirals or arms have newer stars |
| elliptical galaxies | oval shaped, mostly older stars, very little material for new stars |
| Milky Way | our galaxy, is a spiral galaxy |
| light year | distance that light travels in a year, 9.5 trillion kilometers |
| astronomical unit | distance from the Earth to the sun |
