1. Observing the Solar System

2. ??Why is Pluto no longer a planet?? According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit. Pluto has been demoted because it does not dominate its neighborhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons.

3. Ideas of the revolving planets Greek astronomers believed that the Earth is the center of the universe, which is called a geocentric (geo means Earth) system. Copernicus in the 1500’s believed that the sun was the center of the universe, a heliocentric (helio means sun) system. Meaning the planets revolve around the sun.

4. Why do the planets stay in orbit? INERTIA and GRAVITY Inertia is a tendency of a moving object to continue in a straight line or a stationary object to remain in place. The more mass an object has, the more inertia it has. The force of gravity attracts all objects towards each other. No one is for sure how gravity works or why it is present. As the planets are in orbit around the sun the sun’s gravity pulls on them while their inertia keeps them moving ahead.

5. Also known as a “long haired star” in Greek Comets are chunks of ice, gas, water and dust. Comets look like they have tails because as it travels through space it warms up and gives off a cloud of gas around it. They follow an orbit around the sun. As they get closer to the sun they generally speed up.

6. Asteroids After the moons, asteroids are the next largest object in the Solar System. They are irregular shaped, some resemble lumpy potatoes, while others look like rocks. Asteroids are made up of iron, nickel, stone or a combination of them. It is believed that asteroids are actually parts of the solar system that never joined together. Most asteroids are in the asteroid belt, a region that lies between the orbits of Mars and Jupiter. Like comets, asteroids orbit the sun.

7. Meteors – Shooting Stars Meteor– streak of light formed by a space rock and dust burning up as it plunges into Earth’s atmosphere Known as meteoroids when in space.

8. Meteors Cont…….. When and IF this rock strikes Earth it is a meteorite. Most burn up completely before reaching the ground. This occurs when Earth passes through the tail of a comet or a cloud of dust left behind by a broken-up asteroid.

9. Spaced Out Video Clip!

10. Stars Like the sun, stars are huge spheres of glowing gas. They are made up of mostly hydrogen and helium. They make energy by nuclear fusion causing the stars to shine brightly. The main characteristics to classify stars are size, temperature, and brightness.

11. Birth and Death of Stars All stars begin their lives as nebulas, a large amount of gas and dust spread out in an immense volume. Gravity then pulls some of the dust and gas together causing a contracting cloud. A star is born when the contracting gas and dust become so hot that nuclear fusion starts.

12. Birth and Death of Stars How long a star lives depends on how much mass it has. Less massive stars live longer than more massive stars. Stars with less mass than the sun can live up to 200 billion years.

13. When a star begins to run out of fuel, the center of the star shrinks and the outer part of the star expands. It then becomes a red giant or supergiant. After it runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole. A black hole refers to the fact that gravity of black holes is so intense that not even light can escape from them.

14. Black holes http://www.kidsastronomy.com/black_hole.htm http://www.nasa.gov/worldbook/blackhole_worldbook.html http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html When a large star undergoes a supernova explosion it may collapse in on itself. The singularity is a region where the force of gravity is so strong that light cannot escape.

16. Our Star….THE SUN! Our sun is not a very large star, which is a good thing because it will have a longer life- span. It rotates on its axis with an average 25 days for each rotation. The earth is about 1,650,000,000 football fields from the sun ( 150 million km)

17. Our Star….THE SUN! The sun’s core reaches about 15 million degrees Celsius There is enough hydrogen for the sun to last a total of 10 billion years. It is currently about 5 billion years old! The sun’s atmosphere has 3 layers: –Photosphere: Greek word photo means light –Chromosphere: The middle layer. Chromo means color. –Corona: means crown in latin. Like a white halo around the sun and only visible during eclipses or use of special telescopes.

18. Sun spots http://www.suntrek.org/solar-surface- below/sunspots/how-sunspots- formed.shtmlhttp://www.suntrek.org/solar-surface- below/sunspots/how-sunspots- formed.shtml Galileo noticed several black spots on the sun. They are usually found in groups and reappear in the same places about every 11 years.

19. Solar Flares Solar flares are sudden burst of energy in the form of fire. They usually occur over an area of a sunspot. It can give off an extreme amount of radiation The radiation can be harmful to astronauts and disturb radio waves or compasses on Earth.

21. Galaxies Edwin Hubble helped astronomers to begin to understand the huge size of the Universe. We live in the Milky Way Galaxy, a group of about 200 billion stars.

22. Three main classes of galaxies 1. Spiral Galaxy– have arms that spiral outward like pinwheel 2. Elliptical Galaxy– looks like a flattened ball. They lack gas and dust not allowing new stars to form. 3. Irregular Galaxy– does not have a regular shape