fig. 17-1 Relative intensity of the wavelengths of light emitted by bodies with the temperatures indicated. The wavelength of greatest intensity is shorter for hot bodies than for cooler ones. The red curve represents measurements of the sun's photosphere. (1nm = 10^-9 m)

fig. 17-2 The doppler effect in stellar spectra. Star A is stationary with respect to the earth. Star B is moving away from the earth; it moves the distance b during the emission of one light wave, whose wavelength is therefore increased by b. Star C is approaching the earth; it moves the distance c during the emission of one wave, whose wavelength is thus decreased by c. Hence stars receding from the earth have spectral lines shifted toward the red (long-wavelength) end, while stars approaching the earth have spectral lines shifted toward the blue (short-wavelength) end.

fig. 17-3 The proton-proton cycle. This is the chief nuclear reaction sequence that takes place in stars like the sun and cooler stars. Energy is given off at each step. The net result is the combination of four hydrogen nuclei to form a helium nucleus and two positrons.

fig. 17-4 The carbon cycle also involves the combination of four hydrogen nuclei to form a helium nucleus with the evolution of energy. The 12/6 C nucleus is unchanged by the series of reactions. This cycle predominates in stars hotter than the sun.

fig. 17-5 The Big Dipper (a) as it was 200,000 years ago, (b) as it is today (arrow's show directions of motion of the stars), and (c) as it will be 200,000 years from now.

fig. 17-6 The range of stellar sizes, from Antares (at the bottom) through the sun to a large white dwarf (black dot). Neutron stars are even smaller.

fig. 17-7 The Hertzsprung-Russell diagram plots stars according to temperature and intrinsic brightness. The numbers at the left express absolute magnitude (the astronomical measure of intrinsic brightness) with low numbers indicating bright stars and high numbers, faint stars. Masses at right correspond to main-sequence starts. Star colors are indicated at the top.

fig. 17-8 The tendency of a star to contract gravitationally is balanced by the tendency of its hot interior to expand.

fig. 17-9 Life history of a star whose mass is near that of the sun.

fig. 17-10 Life history of a star much heavier than the sun. Such a star spends less time in the main sequence than the star of Fig. 17-9.

fig. 17-11 A comparison of a white dwarf and a neutron star with the sun and the earth. Both white dwarfs and neutron stars are thought to have masses similar to that of the sun.