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# Study Guide - UNIT TEST: Solar System & The Universe 24-25 ## SOLAR SYSTEM ### Inner Planets * The first four planets closest to the Sun: Mercury, Venus, Earth, and Mars * Characteristics: Solid rock. Also called TERRESTRIAL planets; few moons; short orbit around Sun (closer) ### Outer Planets...

# Study Guide - UNIT TEST: Solar System & The Universe 24-25 ## SOLAR SYSTEM ### Inner Planets * The first four planets closest to the Sun: Mercury, Venus, Earth, and Mars * Characteristics: Solid rock. Also called TERRESTRIAL planets; few moons; short orbit around Sun (closer) ### Outer Planets * The last four planets, farthest from the Sun: Jupiter, Saturn, Uranus, & Neptune * Characteristics: Hydrogen & helium; Ring systems are composed of ice, ice-covered rocks and dust; Also called JOVIAN planets; many moons; long orbit around Sun (far away) ### Planet Trivia + Order * **Mercury**: Closest to the Sun; Fastest "Orbital Velocity" (how fast a planet travels around the Sun) * **Venus**: 2nd planet from the Sun; Hottest Planet; known as "Earth's Twin" * **Earth**: 3rd planet from the Sun; Water occurs as a solid (ice), liquid, or gas (water vapor) due to Earth's position in the Solar System; LIFE; Rotation- 1 day (causes day & night-and stars appear to move at night); Revolution- 1 year, (causes the seasons); Axis Tilt = 23.5° * **Mars**: 4th planet from the Sun; Olympus Mons (largest volcano in the solar system) * **Asteroid Belt**: Separates the inner planets from the outer planets; Composed of small, rocky bodies centered roughly between Mars and Jupiter * **Jupiter**: 5th planet from the Sun; Largest planet; Great Red Spot * **Saturn**: 6th planet from the Sun; Largest ring system; * **Uranus**: 7th planet from the Sun; Magnetic field nearly upright (rings are vertical) * **Neptune**: 8th planet from the Sun; Great Dark Spot (Hurricane) * **Pluto**: (Dwarf Planet) - not considered a planet anymore) ## INNER OBJECTS * **Moons**: natural satellites of planets that vary widely in composition * **Meteoroids**: small rocky +iron object floating in space * **Meteor**: Flash you see in the sky (shooting star) * **Meteorite**: object after it hits the Earth * **Meteor Shower**: Caused by comets passing through Earth's orbit * **Comets**: Frozen ammonia, methane, water, chunks of rock & dirt; Comet tails ALWAYS point away from the Sun (because of solar wind)