White-dwarf supernovae are good standard candles for distance measurements for all the following reasons except which?
A) All white-dwarf supernovae involve the explosion of stars of nearly the same mass.
B) White-dwarf supernovae are so bright that they can be detected even in very distant galaxies.
C) White-dwarf supernovae are common enough that we detect several every year.
D) White-dwarf supernovae occur only among young and extremely bright stars.
E) All white-dwarf supernovae have similar light curves, which makes them easy to distinguish from massive-star supernovae.
Question 2
In the equation: Number of Civilizations = Np flife fcivilization fnow what do we mean by fnow?
A) the fraction of planets with civilizations on which the civilizations exist now
B) the fraction of time since the Big Bang represented by the present era
C) the fraction of all species ever to exist that we currently are aware of
D) the fraction of planets in the galaxy on which a civilization could theoretically develop now
E) the fraction of civilizations in the universe that currently are sending messages to us
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