Why is the energy source for active nuclei like Seyferts thought to be compact?
A) The light can vary over short time intervals.
B) Their energy appears to be non-stellar synchrotron radiation.
C) We know the masses of the black holes that lurk there, and can find their radii.
D) They are all strong radio sources, with assigned frequencies by their sizes.
E) The sources appear to be single stars in photos.
Question 2
Which of the following comparisons between low-mass stars and high-mass main-sequence stars is true?
A) Low-mass stars are hotter and more luminous than high-mass stars.
B) Low-mass stars are hotter but less luminous than high-mass stars.
C) Low-mass stars are cooler but more luminous than high-mass stars.
D) Low-mass stars have the same temperature and luminosity as high-mass stars.
E) Low-mass stars are cooler and less luminous than high-mass stars.
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