1. CHARACTERISTICS OF STARS COULTER

2. CLASSIFYING STARS Characteristics used to classify stars include color, temperature, size, composition, and brightness

3. COLOR AND TEMPERATURE A star’s color reveals it temperature. Cooler stars with a surface temperature of 3,200 C appear red. Stars with a surface temperature of 5,800 appear yellow. The hottest starts over 20,000 C appear bluish.

4. SIZE Many stars are about the size of the sun, which is a medium sized star. White dwarfs are about the size of Earth. Neutron stars are about 20KM (smallest) Giant stars and super giant stars. If our sun were a super giant star it would fill our solar system as far out as Jupiter.

5. COMPOSITION Stars vary in chemical composition. Most are about 73% hydrogen, 25% helium, 2% other elements. Spectrograph is a device that breaks light into colors and produces an iage of the resulting spectrum. (most large telescopes have these) Each chemical element absorbs light at particular wavelengths.

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. Star can be described as apparent brightness and absolute brightness. Apparent brightness- its brightness as seen from Earth. Absolute brightness- is the brightness the star would have if it were at a standard distance from Earth. (need to calculate its apparent brightness and distance to get the absolute brightness of a star)

7. MEASURING DISTANCES TO STARS The light-year is a unit astronomers use to measure distances between the stars. Light-year is the distance light travels in one year (about 9.5 million km) Light-year is distance not time: example if it took 1 hour to ride a bike 10 km, you could say it took you 1 bike- year to get to the mall. Parallax: is the apparent change in position of an object when you look at it from different places. Movie theater example: