What is main-sequence fitting?
A) a way of forcing stars to fit into a standard main sequence, even when they have some unusual characteristics
B) a method for determining the age of a star cluster
C) a method for determining the distance to a star cluster by assuming that its main sequence should line up with the main sequence on a standard H-R diagram
D) the way we construct an H-R diagram by plotting the surface temperatures and luminosities of stars
C
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Stars twinkle when seen from Earth. When seen by an astronaut on the Moon, stars
A) twinkle more. B) twinkle less. C) don't twinkle.
The percentage of electricity from nuclear power generated in recent decades in the United States has been about
A) 10%. B) 20%. C) 30%. D) 40%. E) more than 40%
At approximately what time would a first quarter moon rise?
A) 6 P.M. B) noon C) 9 A.M. D) midnight E) 6 A.M.
The force that is exerted by a magnet as it picks up iron nails could be best described as
A) the electric force exerted by electrons in the magnet, on electrons in the nails. B) the force of attraction between the nuclei of atoms in the magnet and the nuclei of atoms in the nails. C) the magnetic force exerted by electrons moving within the magnet, on electrons moving within the nails. D) the electric force exerted by ions in the magnet on electrons in the nails. E) the magnetic force exerted by ions moving within the magnet on electrons moving within the nails.