CH. 4CH. 4Sec. 2 Sec. 2

Characteristics of StarsCharacteristics of Stars

constellationconstellation

• pattern of stars in sky

Orion the Hunter

Can you identify these constellations?

3.

1. 2.

4.

Cygnus the Swan

Pisces the FishGemini the Twins

Hydra the Snake

Main characteristics

Used to Classify

stars

main characteristics

used to classify

stars

Color Temp. size chemical composition

brightness

color & temp.color & temp.• star’s color tells its temp.• range from hottest coolest

–blue or blue-whitewhite red

Colors and Temperatures of Stars video clip

sizesize• smallest largest:1. neutron star

2. white dwarf star

3. medium-sized star

4. giant star

5.supergiant star

spectrographspectrograph

• breaks light into colors & produces image of resulting spectrum

• tells stars:

1. chemical composition

2. temperature

• amount of light given off• depends on size & temp.• described in 2 ways:

brightness

apparent brightnessbrightness as seen from Earth

absolute brightness brightness star would have if it were @

standard distance from Earth

The streetlights in this photo all give off about the same amount of light, and so have about the same absolute brightness.

light year• distance that light travels in 1 year

• = 9.5 million million (trillion) km

You and your friend are sitting behind a woman with a large hat. Why is your view of the screen different from your friend’s view?

Parallax at the Movies

parallaxparallax• method astronomers use to measure

distances to nearby stars

• apparent change in position of an object when you look @ it from different places

Why do nearby stars appear to change position between January and July?

• graph that shows relationship between

surface temp. & brightness

• most stars= main sequence- diagonal line

in ctr. of graph

Hertzsprung-Russell Diagram

The constellation, Orion includes the red supergiant Betelgeuse, the blue supergiant Rigel, and many other main sequence and giant stars.