The Solar SystemWhat’s in Our Solar System?•Our Solar System consists of a central star (the Sun), the nine planets orbiting the sun, moons, asteroids, comets, meteors, interplanetary gas, dust, and all the “space” in between them.•The eight planets of the Solar System are named for Greek and Roman Gods and Goddesses.Inner and Outer Planets•Inner Planets:–Mercury–Venus–Earth–Mars•Outer Planets–Jupiter–Saturn–Uranus–NeptuneThe Relative Size of the Planets in the Solar SystemThe Sun•The sun’s energy comes from nuclear fusion(where hydrogen is converted to helium) within its core. This energy is released from the sun in the form of heat and light.•Remember: Stars produce light. Planets reflect light.

•A star’s temperature determines its “color.” The coldest stars are red. The hottest stars are blue.The 8 Planets of the Solar System•Planets are categorized according to compositionand size. There are two main categories of planets:–Inner Planets: small rocky planets (Mercury, Venus, Earth, Mars)–Outer Planets: gas giants (Jupiter, Saturn, Uranus, and Neptune)Characteristics of the Inner Planets(aka Terrestrial Planets and Small Rocky Planets)•They are made up mostly of rock and metal.

•They are very heavy.•They move slowly in space.•They have no rings and no more than 2 moons (if any).•They have a diameter of less than 13,000 km.Mercury•Closest planet to the Sun.•Smallest planet.•Has craters like our moon.•No moons orbit Mercury.

•Has a revolution period of 88 days. Mercury has extreme temperatures, ranging from 800?F (daytime) to -270?F (nighttime).•Even though it is the closest planet to the sun, Scientists believe there is ICE on Mercury! The ice is protected from the sun’s heat by crater shadows.Venus•2ndPlanet from the Sun.•Venus is the brightest object in the sky (after the sun and moon) because its atmosphere reflects sunlight so well. People often mistake it for a star.•Its maximum surface temperature may reach 900?F.

•Venus has no moons and takes 225 days to complete an orbit around the Sun.•Closest in size to Earth.•Has more than 1,000 volcanoes.Earth•3rdplanet from the Sun. •Earth is the onlyplanet known to support living organisms.•Earth’s surface is 71% water.

–Water is necessary for life on Earth.–The oceans help maintain Earth’s temperatures.•Earth has one moon and an oxygen rich atmosphere.

Earth’s Moon•It takes the moon approximately 29 days to complete one rotation. The same side of the moon always faces us.•The moon’s surface is covered in dust and rocky debris from meteor impacts. It has no water or atmosphere. •The moon reflects light from the sun onto the earth’s surface.

•4thPlanet from the Sun.•Like Earth, Mars has ice caps at its poles. •Mars has the largest volcano in our solar system: Olympus Mons •Mars appears red because of iron oxide, or rust, in its soil.•Mars has two moons and takes about two years to complete an orbit.

•Giant dust storms often cover Mars.MarsCharacteristics of the Outer Planets(aka Gas Giants)•They are made up mostly of gases (primarily hydrogen ; helium).•They are very light for their size.•They move quickly in space.•They have rings and many moons.•They have a diameter of less than 48,000 kmJupiter•5thPlanet from the Sun.

•The largest planet.•It’s diameter is 11 times bigger than that of the Earth’s. •About12 years for Jupiter to orbit the sun.

•Jupiter has 53 known moons.•Great Red Spot –a circular storm on the planetSaturn•6thPlanet from the Sun.•Saturn is made of almost entirely of hydrogen and helium.

•2ndlargest planet.•Saturn has thousands of rings made of ice, rock, and dust. •Saturn has 53 confirmed moons, some of which orbit inside the rings!•It takes Saturn about 30 years to orbit the sun.Uranus•7thPlanet from the Sun.•Uranus is blue because of methane gas in its atmosphere.

•Uranus has 13 faint rings surrounding it. •Uranus has 27 confirmed moons •Takes 84 years to complete one orbit around the Sun.•It rotates on its side.•Coldest planet.Neptune•8thPlanet from the Sun.

•Neptune has the fastest winds in the solar system•Has a circular storm like Jupiter•Neptune is also blue in color due to methane gas in its atmosphere.•Neptune takes 165 years to orbit the sun•Has 13 confirmed moons.Pluto•Pluto has only one moon and takes about 249 years to orbit the sun. •Part of Pluto’s orbit passes inside that of Neptune, so at times Neptune is the planet farthest from the sun.•Pluto was located and named in 1930, but today Pluto is no longer considered a planet.