What makes white-dwarf supernovae good standard candles?
A) They are very bright, so they can be used to determine the distances to galaxies billions of light-years away.
B) They should all have approximately the same luminosity.
C) They occur so frequently that we can use them to measure the distances to virtually all galaxies.
D) We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately.
E) both A and B
Question 2
Which of the following statements best reflects our current knowledge about the term flife in the equation Number of Civilizations = Np flife fcivilization fnow?
A) The value of flife must be either 0 percent or 100 percent.
B) The value of flife is between 0 percent and 100 percent.
C) The value of flife is between 0 percent and 1 percent.
D) The value of flife is roughly 50 percent.
E) The value of flife is presently unknown but should be well known within just a few years.
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