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21.2 Characteristics of Stars
Classifying Stars
Learning Target: I can ___________________________________________
Key Concept: Characteristics used to classify stars include _________,
________________, _________, ______________, and ______________.
 A star’s ________ gives clues about the star’s temperature. The coolest
stars appear ________. The hottest stars appear ________.
 Very large stars are called ________ stars or ____________ stars. Our sun
is a medium sized ________. Most stars are ________ than the sun. White
dwarf stars are about the size of ________. Neutron stars are even
___________, only about 20 km in diameter.
 Stars differ in their chemical makeup. Most stars are about ____% hydrogen,
____% helium, and ____% other elements. Astronomers use a spectrograph, a
device that breaks light into ________, to find out what elements are in a
star. By comparing a star’s spectrum with known elements, astronomers can
infer how much of each ________ is in the star.
Use the ideas above and your textbook to answer the following questions:
1. Five characteristics astronomers use to classify stars are:
___________________________________________________________
2. Stars that appear red are very ________.
3. Stars that appear blue are very ________.
4. The smallest stars in our universe are called ___________ _______.
5. Our sun is a ___________ size star.
6. Most stars have a chemical composition that is 73% _____________,
25% ____________ and 2% ________________
7. A device that breaks light into colors is called a ______________________.
Spectral Class
Surface Temperature (K)
Color
Examples
O
>30,000
Violet-blue
Naos
Mintaka
B
10,000-30,000
Blue
Spica
Rigel
A
7,500-10,000
White
Vega
Sirius
F
6,000-7,500
Yellow-white
Canopus
Procyon
G
5,000-6,000
Yellow
Sun
Capella
K
3,500-5,000
Orange
Arcturus
Albederan
M
3,500
Red
Antares
Betelgeuse