Although Pluto is no longer considered a planet, it is still part of the solar system.

Solar Nebular Theory

• A nebula is a cloud of gas and/or dust in space.

• According to the nebular theory, the sun and planets formed from a rotating disk of dust and gases.

• Planetesimals are small, irregularly shaped bodies formed by colliding matter.

Planetary Composition, Distance from the Sun, and Melting Point

• INNER PLANETS–also known as the terrestrial planets

–dense, small, have solid rocky surfaces, metal cores

•OUTER PLANETS–also known as the Jovian Planets

– less dense, large, gaseous, thick atmosphere

“My Very Eager Mother Just Served Us Noodles”

To remember the order of the planets, just remember this sentence…

Solar System Models

•geocentric model: model of the solar system that states that the Earth is the center of the solar system–believed until 1600’s

•heliocentric model: model of the solar system that states that the sun is the center of the solar system and the planets revolve around it

•The path a planet follows around the sun is called its orbit

Kepler’s Laws of Planetary Motion

•1st law : planets orbit the sun in a path called an ellipse

•2nd law: planets move fastest when they are closest to the sun in their orbits

•3rd law: the farther away a planet orbits, the longer the planet takes to revolve around the sun

•revolution: movement of the Earth around the sun–takes 365.24 days (1 year)

•rotation: spinning of Earth on its axis–takes 24 hours (1 day)–rotates counterclockwise

the Earth is tilted 23 ½ °on its axis. Either the Northern Hemisphere or Southern Hemisphere tilts towards the sun

•hemisphere that tilts towards the sun has summer (more direct sunlight

•hemisphere that tilts away from the sun has winter (less direct sunlight)

•summer solstice: longest sunlight hours of the year-June 21st-first day of summer

•winter solstice: shortest sunlight hours of the year- Dec. 21st- first day of winter

•spring equinox: equal amounts of day/night hours- March 21st- first day of spring

•fall equinox: equal amounts of day/night hours- Sept. 21st- first day of fall

Other Objects in the Solar System

•comet: composed of dust, rock, frozen water, and gas

1. nucleus: glows by reflected sunlight

2.coma: hazy cloud that surrounds the nucleus

3. tail: gas and dust that always points away from the sun

Halley’s Comet

Hale-Bopp Comet

•asteroid: solid, rock-like mass, irregular in shape

•orbit the sun- most orbit between Mars and Jupiter in the asteroid belt

•meteoroid: rock or icy fragment moving through space–can be large as a boulder or as small as sand

•meteor: light made by meteoroid as it passes through Earth’s atmosphere

iron meteorite

stone meteorite

stony-iron meteorite

•if they strike the Earth, they form impact craters (this is rare!)

• Go to www.reviewgamezone.com ; when the page uploads, click on science near the middle at the top of the page. Choose Astronomy which is the first topic. You may select any category you feel will be most helpful to you reviewing. After you choose a topic it will give you a game list. Select and enjoy the game!

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