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Skills Worksheet
INTEGRATING SPACE SCIENCE
Cross-Disciplinary
Starlight, Star Heat
Read the following paragraphs, and complete the exercises below.
Taking the temperature of a star from Earth may seem impossible, but
astronomers can calculate the temperature of a star by measuring its color. The
color of a star is determined by its chemical composition. Each element gives off a
specific light pattern that varies with temperature. To calculate star temperatures,
astronomers use a spectrophotometer—an instrument that breaks starlight into a
spectrum. Different wavelengths appear as different colors.
At one end of the spectrum are the shortest waves. The shortest visible wave
appears violet. As wavelengths increase along the spectrum, the colors are blue,
green, yellow, orange, and red. The longest wavelength of light that humans can
see appears deep red. Astronomers study the star’s spectrum and compare it to
data obtained from laboratory measurements to determine a star’s chemical
makeup and temperature.
Astronomers often classify the spectrum of stars by the letters O, B, A, F, G, K,
and M. Each letter represents a class of spectrum, which is related to its
temperature. The table below lists representative temperatures and colors of
various classes of stars.
Spectral class
Temperature (C°)
Color
O
B
A
F
G
K
M
35,000
21,000
10,000
7,000
6,000
4,500
3,000
blue-white
hot white
cool white
creamy
yellow
orange
red
EXERCISES
1. The longest wavelengths are associated with which temperatures, the hottest or
the coolest?
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2. Our sun appears to be yellow. To which spectral class does the sun belong?
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3. Write a generalization that states the relationship between star temperature, the
colors blue and red, and wavelength.
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science Spectrum
21
Heat and Temperature