1. Characteristics of Stars

2. What is a galaxy? (hundreds of billions of stars) (hundreds of billions of stars) Our solar system is located in the Our solar system is located in the * Our galaxy is named the Milky Way because of it’s white milky color. Not because of the candy bar!!!! It is a cluster of stars Milky Way Galaxy Milky Way Galaxy

3. What is the Universe? Consists of billions of galaxies. Consists of billions of galaxies. Most of the Universe is empty space, due to everything being soooooo far apart! Most of the Universe is empty space, due to everything being soooooo far apart! All of space and everything in it!!!! All of space and everything in it!!!!

4. Distances to Stars Instead of using kilometers, astronomers use a unit called. Instead of using kilometers, astronomers use a unit called. A light year is the distance. A light year is the distance. * If we wanted to travel to the center of the Milky Way it would take 25,000 years traveling at the speed of light. That is a distance of 250 million billion kilometers. light-year. light travels in one year or 9.5 million million kilometers. light travels in one year or 9.5 million million kilometers.

5. Measuring Distances to Stars Parallax- apparent change in position of an object when you look at it from different places. (Thumb example) Parallax- apparent change in position of an object when you look at it from different places. (Thumb example) Astronomers use the to measure distance to stars: Astronomers use the to measure distance to stars: First they observe a star & then observe it again 6 months later. First they observe a star & then observe it again 6 months later. The less the star moved the The less the star moved the the star moved the closer it is the star moved the closer it is parallax shift further away it is The more

6. Classifying Stars Three main characteristics: Three main characteristics: Size Temperature and color Brightness

7. Size

8. Color & Temperature A star’s color reveals A star’s color reveals are the hottest (15,000 degrees Celsius) are the hottest (15,000 degrees Celsius) Rigel Rigel are the coolest (3,200 degrees Celsius) are the coolest (3,200 degrees Celsius) Betelgeuse Betelgeuse its temperature Stars that glow blue-white Stars that are red

9. Brightness Brightness of a star depends on its Brightness of a star depends on its How bright a star is also depends on its f from Earth. How bright a star is also depends on its f from Earth. Brightness is described in two different ways: Brightness is described in two different ways: size and temperature. size and temperature. distance Apparent magnitude Absolute magnitude

10. Brightness Apparent Magnitude- Apparent Magnitude- Brightness as seen from Earth. Brightness as seen from Earth. Ex. Sun looks very bright but this does not mean the sun gives off more light than other stars. It just means it is closer to Earth. Absolute Magnitude Absolute Magnitude Brightness a star would have if it were at a standard distance from Earth Astronomers determine the apparent magnitude and distance from Earth in order to calculate the absolute magnitude Astronomers determine the apparent magnitude and distance from Earth in order to calculate the absolute magnitude

11. Hertzsprung-Russell Diagram

12. Lives of Stars Stars begin as and dust called a. Gravity pulls the begins. This forms a or ‘new star’ begins. This forms a or ‘new star’ Protostar gas nebula. gas and dust fused together

13. Protostar

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

15. Which means that……….. The smaller the star the_________________ The smaller the star the_________________ It lives. It lives. longer

16. Star Life Cycle Nebula Nebula Protostar Protostar : 90% of stars. Hydrogen continues to burn and fuse to make helium. : 90% of stars. Hydrogen continues to burn and fuse to make helium. Main Sequence

17. MAIN SEQUENCE

18. The star begins to run out of fuel. The star expands. The star begins to run out of fuel. The star expands. Supernova: Supernova: Giant/Super Giant: Massive stars can blow up to an enormous size

19. mass RED GIANT

20. Small and Medium Stars These become giants and then These become giants and then White Dwarfs: When a white dwarf burns out, it is dead. Then it is a blue-white core of a star that is left behind. These have no fuel, but glow faintly from left over energy. Black Dwarf.

21. Super Giants: When a Super Giant explodes into a supernova, it can become 2 things: When a Super Giant explodes into a supernova, it can become 2 things: A. : Smaller and more dense than a white dwarf. They have 3 times as much mass as the sun, but are about the size of Houston! A. : Smaller and more dense than a white dwarf. They have 3 times as much mass as the sun, but are about the size of Houston! Neutron Star

22. Black Hole: Black Hole: Dense area in space that not even light can escape the gravity field. Dense area in space that not even light can escape the gravity field.

23. Super Nova SUPERNOVAexplosion

24. : BLACK HOLE http://chandra.harvard.edu/photo/2004/rxj1242/index.html

25. Nebula  Protostar  Nebula  Protostar  Main Sequence  Giant or Supergiant  Giant or Supergiant  White Dwarf Supernova White Dwarf Supernova Neutron Star Neutron Star Black Dwarf Black Dwarf OR OR Black Hole Black Hole

26. Binary Star Systems Sometimes this causes stars to appear Sometimes this causes stars to appear Stars that revolve around each other. as if they are blinking as if they are blinking

27. Let’s Review! 1. All stars begin as gas and dust called a. Protostar b. Nebula c. White dwarf

28. 2. Most stars are in this stage a. Protostar b. White Dwarf c. Main Sequence

29. 3. The life of a star depends on its a. Color b. Place in the universe c. Mass

30. 4. If the star is super massive, it will live longer. a. True b. False

31. 5. Low mass stars will become black holes a. True b. False

32. 6. An object so dense, not even light can escape. a. Supernova b. Main Sequence c. Black Hole d. Nebula

33. 7. A new star where fusion begins. a. Protostar b. Neutron Star c. Main Sequence