| A | B |
|---|
| heliocentric | solar system where planets revolve around the sun |
| geocentric | solar system where planets revolve around the earth |
| solar_system | system comprised by revolving planets, satellites, comets and meteoroids |
| Copernicus | Polish astronomer who developed heliocentric model of the solar system |
| Kepler | German astronomer who thought planets revolved around the sun in ellipses |
| Galileo | Italian astronomer who observed Jupiter's moons |
| aphelion | orbital location where a planet is farthest from the sun |
| perihelion | orbital location where a planet is nearest to the sun |
| gravity | force of attraction between two or more objects |
| Newton | English scientist who mathematically described the force of gravity |
| centripetal | inward force that keeps objects moving in a circular motion |
| solar_nebula | gaseous mass that gives birth to stars |
| protostellar | rotating disk of hydrogen gas that eventually forms into a sun |
| planetesimals | large rocky bodies that collide and merge eventually forming planets |
