1. Characteristics Of Stars Galaxy: A collection of stars, gases and dust. Universe: Contains billions of galaxies.

2. The Milky Way galaxy has a whopping circumference of roughly 250-300 thousand light years! Within the main body of the Milky Way there are estimated to be between 200 and 400 billion stars.

3. Types of Galaxies 1. Spiral 2. Elliptical 3. Irregular

4. Spiral Galaxies: Arms spiral outward like a pinwheel Our galaxy, The Milky Way, is a spiral galaxy

6. Elliptical Galaxies: Look like flattened football. Have billions of stars, but little gas and dust. Contain the oldest galaxies

8. Irregular Galaxies No definite shape Example: Large Magellanic Cloud

10. ( Light will travel 10 trillion kilometers in one year!) Scientists use LIGHT YEARS to measure distances in space. A light year is the distance light travels in one year. Light travels at the speed of 300,000,000 meters/second.

11. Classifying Stars Stars are classified by 3 Main Characteristics: 1. Size 2. Temperature 3. Brightness

12. Hottest (20,000-50,000*C) : (10,000*C) (6,000*C) (4,000-5,000*C) (3000*C) Color reveals the temperature of a star.

13. Brightness of Stars Apparent Magnitude: Brightness as seen from earth Absolute Magnitude: Brightness of a star from a standard distance

14. Hertzsprung-Russell Diagram A graph plotting brightness and temperature. 90% of stars are Main Sequence

16. Solar flare

21. Overview of Star Life Cycle

22. Lifetimes of Stars A star’s life depends on its mass. Stars smaller than the sun live up to 200 billion years. Medium sized stars like the sun live around 10 billion years. Stars 15 times more massive than the sun live about 10 million years.

23.  Clouds of gas – made up of elements and compounds  As they spin and condense, heat energy is transformed, forming stars NEBULA

29.  Medium sized star  By speed of light, only takes 8.3 minutes to get to Earth from the Sun  Located on the edge of a spiral of the Milky Way galaxy  Center of Solar System SUN

34.  Dense gravity well in space  Light cannot escape the gravitational pull of a black hole  Observed because astronomers can see light and energy being given off by objects being pulled into them  No volume, infinite density  Could be a result of a Supernova explosion BLACK HOLE

38. http://chandra.harvard.edu/resources/flash/bh_ truth.html