1. Classifying Stars
Color
Temperature
Size
Composition/Mass
Brightness

2. Less than the distance to school
Size Comparison
Size Classification
Approximate Size (km)
Examples
Neutron Star
16 km
Less than the distance to school
pulsar
White Dwarf
Less than the distance across Asia
Sirius B
Van Maanen’s star
Medium star
109 X size of Earth or 1,392,000 km
Sun
Giant star
100 X size of Sun
Aldebaran
Supergiant
1000 X size of Sun
Rigel, Betelgeuse, Arcturus

4. Color and Temperature Star Color Surface Temp (oC) Blue or Blue-White
Yellow
6,000 oC
Red-Orange
5,000 oC
Red
3,000 oC

5. Chemical Composition Most stars are made of 73% Hydrogen 25% Helium
2% Other elements
Astronomers use spectrographs to determine elements found in stars
Spectrograph is a device that breaks light into colors and produces an image of the resulting spectrum

6. Brightness of Stars
The brightness of a star depends upon both its size and temperature
How bright a star looks from Earth depends on both its distance from Earth and how bright the star truly is

7. Brightness of Stars
Apparent magnitude- The brightness of a star as it appears on Earth
Absolute magnitude- The amount of light a star actually gives off (uses formulas)

8. Why do stars twinkle?
The scientific name for the twinkling of stars is stellar scintillation
Stars twinkle when we see them from the Earth's surface because we are viewing them through thick layers of turbulent (moving) air in the Earth's atmosphere.

9. Measuring Distances to Stars
Astronomers use a unit called the light year to measure distances between the stars
Light travels at a speed of 300,000 km/s
Light year- distance that light travels in one year =9.5 trillion km
Light year=unit of distance

10. Parallax Astronomers use parallax to measure distances to nearby stars
Parallax= the apparent change in position of an object when viewed from two locations

11. Parallax is larger for closer objects