 Our solar system includes the sun, the planets and many other smaller objects  Astronomers use astronomical units to measure distances in our solar system  An astronomical unit (AU) is the average distance between the Earth and the sun or 150 million kilometers

The solar system is divided into two main parts -Inner Solar System -Outer Solar System

 Inner Solar System =  Mercury, Venus, Earth and Mars  All smaller and terrestrial planets

 Outer Solar System =  Jupiter, Saturn, Uranus, Neptune  All larger gas giants  These planets are furthest from the sun

Vocabulary Review:  Period of Revolution- Time it takes for a planet to make one revolution around the sun. This is called a year.  Period of Rotation- Time it takes for a planet to make one revolution on its axis. This is called a day

Vocabulary Review:  Period of Revolution- Time it takes for a planet to make one revolution around the sun. This is called a year.  Period of Rotation- Time it takes for a planet to make one revolution on its axis. This is called a day

Vocabulary cont.  NEBULA – a large cloud of gas and dust in interstellar space  Two forces interacting in nebulas: 1. Gravity 2. Pressure

What’s going on in a planetary nebula?  GRAVITY causes the particles in a nebula to be attracted to each other.  As particles move close together, collisions cause PRESSURE to increase and particles are pushed apart  If the inward force of gravity is balanced by outward pressure, the nebula becomes stable.

What’s going on in a planetary nebula?  The balance between gravity and pressure can be upset by:  Two nebulas colliding  A nearby star explodes  When the balance is upset – small regions of the nebula are compressed and form GLOBULES (GAS CLOUDS)

What’s going on in a planetary nebula?  Globules - very dense - contract under their own gravity – collapses inward  Temperature increases - THE STAGE IS SET FOR STAR FORMATION  SOLAR NEBULA – the cloud and dust that formed our solar system

HOW THE SOLAR SYSTEM FORMED 1. Young solar nebula BEGINS TO COLLAPSE – it took about 10 MILLION years for the solar system to form. 2. The solar nebula rotates, flattens, and becomes warmer near its center. 3. PLANETESIMALS begin to form WITHIN THE SWIRLING DISK.

 A PLANETESIMAL is a small planet 4. As the largest planetesimals grow in size, their gravity attracts more gas and dust. 5. The smaller planetesimals collide with the larger ones, and planets begin to grow. 6. A star is born, and the remaining gas and dust are blown out of the new solar system.

 Closer to the center of the nebula temperatures were TOO HOT for gases to remain  Therefore the inner planets are made mostly of ROCKY MATERIAL.

Revolution:.24 years Rotation: days Moons: 0 Radius:.382 of Earth Mass:.06 of Earth Atmosphere: essentially no atmosphere Missions: MESSENGER completes flybys (2008) Other Info.:  Similar in appearance to our Moon because of it’s crater filled surface.  Difficult to see from the Earth’s surface because of its proximity to the Sun. Named for the Roman God’s messenger known for speed Type: Terrestrial

Revolution:.62 years Rotation: days Moons: 0 Radius:.949 of Earth Mass:.82 of Earth Atmosphere: CO 2 N 2 (intense greenhouse effect) Missions: Magellan orbits Venus Other Info.:  Venus is the hottest planet in the solar system  Has active volcanoes Named for the Roman Goddess of Love and Beauty Type: Terrestrial

Revolution: 1 year Rotation: 1 day Moons: 1 Radius: 6371 km Mass: 5.97 x kg Atmosphere: N 2 O 2 Missions: n/a Other Info.:  We live here!  Only planet we know of (at this time) with complex life  “Goldilocks” planet Type: Terrestrial

Revolution: 1.88 years Rotation: 1.03 days Moons: 2 (Phobos, Deimos) Radius:.532 of Earth Mass:.11 of Earth Atmosphere: CO 2 N 2 (thin) Missions: the most recent mission is the Mars Curiosity although we have had several non-manned missions to the red planet Other Info.:  Mars has frozen CO 2 at its poles  Possibly had liquid water at some point  Largest volcano in the entire solar system: Olympus Mons Named for the Roman God of War Type: Terrestrial

 Ceres is located here (an asteroid large enough to attain the gravitational force to become spherical – making it a dwarf planet)  All matter in asteroid belt = 1/10 of our moon  Located between Mars and Jupiter  Left over “scrap” material from the formation of our solar system.

 The largest planetesimals formed near the outside of the rotating solar disk, where hydrogen and helium were located.  These outer planets grew to huge sizes and became gas giants (can also be separated into gas and ice giants)

Revolution: years Rotation:.41 days Moons: 67 Radius: of Earth Mass: of Earth Atmosphere: H 2 He (intense storms) Missions: Juno is slated to arrive in 2016 Other Info.:  The banded appearance of Jupiter is due to the clouds stretching around the globe as the planet spins more rapidly than the Earth  The moon Europa is a good candidate for the search for life in our solar system  Has a ring system Named for the Roman King of the Gods (Zeus in Greek myth) Type: Gas Giant

Revolution: years Rotation:.43 days Moons: Radius: of Earth Mass: of Earth Atmosphere: H 2 He Missions: Cassini currently orbits Saturn Other Info.:  Saturn’s rings are composed mostly of icy water and rocks. There are only a few gaps, some due to the orbits of Saturn’s moons.  2 of the Moons, Titan and Enceladus are good candidates in the search for extraterrestrial life. Named for the Roman God of agriculture Type: Gas Giant

Revolution: years Rotation: -.72 days Moons: 27 Radius: of Earth Mass: of Earth Atmosphere: H 2 He Missions: Voyager 2 passed by Other Info.:  The blue-green appearance is caused be methane gas  While still composed of H and He Uranus also possesses water, methane and ammonia  Has the coldest of all planetary atmospheres in our solar system  Its axis is tilted sideways possibly from a collision  Has a ring system Named for the Roman God of the Sky Type: Ice Giant

Revolution: years Rotation:.67 days Moons: 13 Radius: of Earth Mass: of Earth Atmosphere: H 2 He Missions: Voyager 2 passed by Other Info.:  White clouds are composed of methane ice while the blue color is partially due to the methane absorbing red light.  Similar in composition to Uranus  Active weather patterns  Faint and fragmented ring system “arcs” Named for the Roman God of the Sea Type: Ice Giant

 According to the International Astronomical Union, which sets definitions for planetary science, a dwarf planet is a celestial body that:  Orbits the sun.  Has enough mass to assume a nearly round shape.  Has not cleared the neighborhood around its orbit.  Is not a moon.  The main distinction between a dwarf planet and a planet is that planets have cleared the path around the sun while dwarf planets tend to orbit in zones of similar objects that can cross their path around the sun (like asteroids). Dwarf planets also are generally smaller than the planet Mercury.