1. Characteristics of Stars

2. Color, temperature, size, composition, and brightness Color shows a stars surface temperature. Blue stars are hot with surface temp of 20,000 degrees Celsius! Red stars are coolest with surface temp. of 3,200 degrees Celsius 5 characteristics used to classify stars How are stars classified by color and temperature?

3. Characteristics of Stars Stars vary greatly in size. 73% hydrogen, 25% helium, and 2% other elements How are stars classified by size? What is a star Made of?

4. Characteristics of Stars Spectrograph- device that breaks light into colors and produces an image of the resulting spectrum. How do astronomers determine elements found in stars? Hubble Space telescope

5. Characteristics of Stars Depends upon both its size & temperature. Two ways to describe brightness of Star apparent brightness and absolute brightness. What does the brightness of a star depend on? What two ways determine a stars brightness?

6. Characteristics of Stars brightness seen from Earth brightness the star would have if it were at a standard distance from Earth. apparent brightness Absolute brightness

7. Characteristics of Stars Distance that light travels in one year, about 9.5 million million kilometers – Used to measure distances between stars. Definition of Light year apparent change in position of an object when you look at it from different places. Definition of parallax

8. Characteristics of Stars Graph showing the relationship between surface temp. and absolute brightness of stars. - used to classify stars and understand how stars change over time. Hertzsprung- Russell diagram main sequence Diagonal area on an H-R diagram that includes more than 90% of all stars.