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# Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn

Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation?
a)It will allow us to calculate the rotation rate of the galaxy.
b)We can learn the distance to the galaxy.
c)It will allow us to determine the mass of the galaxy.
d)Under the rules of the International Astronomical Union, we will be entitled to naming rights for the galaxy.

Suppose that Hubble's constant were 20 kilometers per second per million light-years. How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is due only to Hubble's law.)
a)away from us at 2,000 km/s
b)away from us at 20,000 km/s
c)away from us at 200 km/s
d)toward us at 2,000 km/s

Hubble's constant is about 22 km/s/million light-years, implying an age of about 14 billion years for the universe. If Hubble's constant were 11 km/s/million light-years, the age of the universe would be about _______.
a)Impossible to say, because Hubble's constant has no relationship to the age of the universe.
b)28 billion years
c)7 billion years
d)14 billion years

Please and thank you! (trying to study for midterm tmrw)

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