Order of the Planets What is an AU? Inner vs. Outer Planets Other stuff in our Solar System

 The sun is the biggest, brightest, and hottest object in the solar system.  The sun is an ordinary star.  The sun is made of about 70% hydrogen and 28% helium.

 Mercury is solid and is covered with craters.  Mercury has almost no atmosphere.  Mercury is the eighth largest planet.

 Venus is the sixth largest planet. It’s about three-fourths the size of earth.  The surface is rocky and very hot. The atmosphere completely hides the surface and traps the heat.

 Earth is the fifth largest planet and the third from the sun.  Liquid covers 71 percent of the Earth’s surface.  The Earth has one moon.

MMars is the fourth planet from the sun. MMars has a thin atmosphere that contains mostly carbon dioxide. MMars has two small moons.

Phobos Deimos

TThe Great Red Spot, a huge storm of swirling gas that has lasted for hundreds of years. JJupiter does not have a solid surface. The planet is a ball of liquid surrounded by gas.

Jupiter has four large Galilean moons, twelve smaller named moons and twenty- three more recently discovered but not named moons. We’ll take a look at the four large Galilean moons which were first observed by Galileo in 1610.

Io is the fifth moon of Jupiter. It’s the third largest of Jupiter’s moons. Io has hundreds of volcanic calderas. Some of the volcanoes are active.

 Europa is the sixth of Jupiter’s moons and is the fourth largest.  It is slightly smaller than the Earth’s moon.  The surface strongly resembles images of sea ice on Earth. There may be a liquid water sea under the crust.  Europa is one of the five known moons in the solar system to have an atmosphere.

 Ganymede is the seventh and largest of Jupiter’s known satellites.  Ganymede has extensive cratering and an icy crust.

 Callisto is the eighth of Jupiter’s known satellites and the second largest.  Callisto has the oldest, most cratered surface of any body yet observed in the solar system.

 Saturn is the second largest planet and the sixth from the sun.  Saturn is made of materials that are lighter than water. If you could fit Saturn in a lake, it would float!

 Saturn’s rings are not solid; they are composed of small countless particles.  The rings are very thin. Though they’re 250,000km or more in diameter, they’re less than one kilometer thick.

 Uranus is the third largest planet and the seventh from the sun.  Uranus is one of the giant gas planets.  Uranus is blue-green because of the methane in its atmosphere.

 Neptune is the fourth largest planet and the eight from the sun.  Because of the orbits, from 1979 to 1999, Neptune was the ninth planet.  Like Uranus, the methane gives Neptune its color.

 Pluto is the smallest planet and usually the farthest from the sun.  Pluto is the only planet that has not been visited by a spacecraft.

 An AU: Astronomical Unit, is what scientists have defined as the distance between the Earth and Sun. ~150,000,000 Kilometers  Earth to Sun = 1 AU  < 1 AU = Closer to Sun than Earth  > 1 AU = Further from Sun than Earth

 Inner planets Mercury Venus Earth Mars  Outer Planets Jupiter Saturn Uranus Neptune Separated by the asteroid belt

 Inner Planets  Outer Planets Solid Crust More Dense Few or no Moons Smaller- less gravity Closer to the Sun Short Revolution Longer Rotation No Rings Warmer Gaseous (not solid) Less Dense Many Moons Larger- more gravity Farther From the Sun Longer Revolution Shorter Rotation Rings Colder Orbit the Sun (Duh!) Rotate on an Axis Gravity Round Atmosphere Mercury, Venus, Earth MarsJupiter, Saturn, Uranus, Neptune

 Remnants of the formation of the Solar System Between Mars and Jupiter (separates the inner planets from the outer ones) about AU from the Sun Made mostly of rock and metal like the inner planets

Remnants of the formation of the Solar System Beyond the orbit of Neptune (after the outer planets) About 50 AU from the Sun Bigger than the asteroid belt composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. The Kuiper belt is home to dwarf planets such as Pluto

 Asteroids made up of metals and rocky material formed much closer to the Sun where it was too warm for their ices to remain solid Asteroids also tend to group together in belts – as evidenced by the massive one that lies between Mars and Jupiter in our Solar System many millions of asteroids – some as small as dust particles and others measuring hundreds of kilometers across  Comets comets are made up of ice, dust and rocky material comets formed far away from the sun  As they get closer to the sun they form a “tail” as the ice melts but continues as the same velocity as the comet Comets tend to have very extended and elongated orbits, which often exceed 50,000 AU from the Sun. There are only 3,572 known comets