Planet Bellringer Complete questions a-g on the sheet taped to your desk in your composition notebook

IV. Characteristics of Stars

A. Distance to Stars 1. Light year. -Is the distance that a ray of light travels in year. Ex. Centauri is 4.3 LY away. While Betelgeuse, the red supergiant of Orion’s belt is 490 LY. Speed of light= 299,792,458 m/s

2. Circumpolar constellations- constellations you see all year a. Ursa Major, Ursa Minor, Draco, Cassiopeia, Cepheus

B. Physical properties of stars 1. Size a. mass- small burn slowly, large burn quickly. Ex. The smallest may be smaller than Earth. The largest is 2000 times larger than the sun.

2. Color & Temperature 3. Chemical Composition - Depends on surface temperatures. a. Hot stars are bluer in color. Cool stars are redder in color. Most hydrogen & helium a. Every element has a unique “fingerprint.”

4. Brightness or Luminosity - Depends on size & temperature

C. Hertzsprung-Russell Diagram 1. Use 2. Basis - Classify stars & understand how stars change over time. - Plots temperature vs. luminosity

90% of all stars

H-R Diagram Questions: Describe the size of stars in the H-R diagram (in comparison with the sun) in the upper right portion. Describe the color of the stars in the upper right portion of the H-R diagram. Describe the size of stars in the H-R diagram (in comparison with the sun) in the upper left portion. Describe the color of the stars in the upper left portion of the H-R diagram. Describe the size of stars in the H-R diagram (in comparison with the sun) in the lower right portion. Describe the color of the stars in the lower right portion of the H-R diagram. Describe the size of stars in the H-R diagram (in comparison with the sun) in the lower left portion. Describe the color of the stars in the lower left portion of the H-R diagram. Where in the H-R diagram would you find a star the same size and color as our sun? What is the classification of the Sun? How would you classify the brightest stars? (they may be in more than one star class.) Describe the difference between stars Sirius A and Betelgeuse. Name the brightest star on your diagram. Name the “coolest” star on your diagram. Describe the movement of the Sun’s life cycle through the H-R diagram.