| A | B |
|---|
| solar system | the sun & all of the planets & other bodies that travel around it |
| planet | a celestial body that orbits the sun; round because of own gravity; has cleared the neighborhood around its orbital path |
| solar nebula | rotating cloud of gas & dust from which the sun & planets formed |
| planetesimal | a small body from which a planet originated in the early stages of development of the solar system |
| eccentricity | the degree of elongation of an elliptical orbit |
| orbital period | the time required for a body to complete a single orbit |
| inertia | tendency of an object to resist being moved-if the object is moving, to resist a change in speed or direction until outside force acts on it |
| terrestrial planet | one of the highly dense planets nearest to the sun; Mercury, Venus, Mars, Earth |
| gas giant | a planet that has a deep massive atmosphere, such as Jupiter, Saturn, Uranus or Neptune |
| Kuiper Belt | a region of the solar system that starts just beyond the orbit of Neptune & contains dwarf planets & other small bodies made mostly of ice |
