1. Review Day Drill: What celestial object is described as a “dirty snowball” and why? Objective: SWBAT review concepts presented in the first unit of Astronomy in order to prepare for Thursday’s test. HW: Test Thursday

2. Our Solar System My Very Energetic Mother Just Served Us Nachos Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

3. Astronomy Unit 1 Review History of Our Solar System  Ptolemy: Geocentric model placed Earth at the center of the solar system. Planets orbited in little circles on a bigger circle.  Copernicus: Heliocentric model placed the sun in the center but planets orbited in perfect circles.  Kepler: Created the modern day model of the solar system. Heliocentric with elliptical orbits.

4. Orbits Planets orbit the sun in an elliptical shape. A combination of Inertia and Gravity cause the shape. Inertia: The force of a moving object to resist change speed or direction. Gravity: Attraction between two objects affected by 2 things.  Distance: the closer you are the stronger the force.  Mass (weight): the heavier the object the greater the force.

5. Nebular Theory The solar system formed from a large cloud of gas and dust called a NEBULA A concentration of mass in the nebula created an imbalance and caused the cloud to collapse and spin. As more matter moved to the center the material began to spin more rapidly creating a bulge in the center and a flattened disk.

6. Nebular Theory con’t Material in the disk separated by density/mass. Heavier materials were pulled close to the sun forming the inner planets. Lighter materials gravitated to out to form the outer planets.

7. Inner and Outer Planets Inner planets are:  Terrestrial: made of rock and metal  Small  Hot  Orbit close together  Closer to the sun Outer planets are:  Gas: Mostly Hydrogen.  Large  Cold  Orbit far apart  Farther from the sun

8. Comets and Asteroids Comets are:  “Dirty snowballs” made of ice, gas, dust, and rock.  Have a head called the nucleus and a halo called the coma.  Have a tail.  Found in the Oort cloud and Kuiper belt. Asteroids are:  Made of rock and metals.  Mostly found in the asteroid belt between Mars and Jupiter.

9. The Breakdown of Meteoroids Meteoroids: Broken pieces of Asteroids and Comets in space. Meteors: Meteoroids that enter the Earth’s atmosphere causing streaks. Meteorites: A meteoroid that passes through the Earth’s atmosphere and reaches the Earth’s surface.