Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?
A) The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists.
B) Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4-solar-mass limit.
C) White dwarfs get hotter with increasing mass, and above the 1.4-solar-mass limit they would be so hot that even their electrons would melt.
D) White dwarfs are made only from stars that have masses less than the 1.4-solar-mass limit.
B
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Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude?
A) Rigel has a higher surface temperature than Sirius. B) Rigel has a higher core temperature than Sirius. C) Sirius has a higher core temperature than Rigel. D) Sirius has a higher surface temperature than Rigel.
Which of the following statements about Kepler's laws is false?
A) Kepler's laws provide mathematical descriptions of the motion of the planets. B) Kepler's first law states that planetary orbits are shaped as ellipses. C) Kepler's second law implies that when planets are closer to the sun, they move faster. D) Kepler's laws explain why planets with larger semi-major axes have much longer orbital periods.
Solar power is commonly used to produce
A) heat. B) electricity. C) both of these
How are radio waves generated? How are they detected? What do you think limits the highest radio frequency that can be generated?