Sunspots are cooler than the surrounding gas in the photosphere because
A) they are regions where convection carries cooler material downward.
B) there is less fusion occurring there.
C) magnetic fields trap ionized gases that absorb light.
D) strong magnetic fields slow convection and prevent hot plasma from entering the region.
E) magnetic fields lift material from the sunspot and quickly cool the material.
D
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Write the governing equation and the necessary boundary conditions for the problem of a heat exchanger tube as shown in Figure 2-54.
The youngest stars in the Orion Nebula and other star-forming regions also show
a. circumstellar disks. b. jets. c. circumstellar disks and jets.
Assuming that xenon (atomic number 54) and krypton (atomic number 36) have the same temperature and pressure, in which gaseous medium does sound travel faster?
A) Xenon B) Krypton C) a mixture of both D) the same in both
The mass of the Milky Way Galaxy can be estimated by:
A) the orbital motions of the stars within the galaxy. B) the mass of the planets in the Solar System. C) the luminosity of the stars of the neighboring galaxies. D) the concept laid down by the spiral density wave theory.