1. Characteristics of Stars p. 775 - 780
Chapter 30
Characteristics of Stars p

2. What is a star? Body of gas that gives off light and heat vary in:
color
size
temp,
composition
distance
brightness

3. Analyzing Starlight spectrometers separate light
spectra can tell the composition and temperature of a star

4. Star Composition
Mostly hydrogen and helium

5. Star Temperature
Blue – Hot
Yellow - Medium
Red - Cool

6. Apparent Motion of Stars
Looks like all stars are moving westward around the North Star
Due to earth movement
Circumpolar Stars – circle North star , never go below horizon

7. Actual Motion of Stars
Rotate on Axis
May revolve around another star

8. 3. Revolve around center of galaxy

9. 4. Some Move toward earth (blue shifted) Some move away from earth (red-shifted)

10. Distance to Stars
about 9.5 trillion km/year
300,000 km/s
Measured in LIGHT- YEARS or the distance that light travels in one year

11. Distance to Close Stars (within 1000 light years)
Measured with PARALLAX -shift in the apparent position of the star when viewed from different angles

12. Stellar Brightness Apparent Magnitude
- brightness as it appears from earth
- more negative = brighter

13. 2. Absolute Magnitude – brightness if all stars were the same distance from Earth.