Why is the Hyades Cluster important for building up a catalog of the true luminosities of main-sequence stars?
A) It is close enough to us that the distance to its stars can be found by stellar parallax.
B) It's a cluster that has been photographed over many decades, so we know how the stars vary in brightness.
C) It contains many Cepheid variable stars that can be used to determine its distance.
D) It is an extremely bright star cluster.
E) It is an old globular cluster whose age we can determine very accurately by measuring its main-sequence turn-off point.
A
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A car starts from rest and after 6.0 seconds it has a kinetic energy of 60,000 J. How much horsepower is needed for the car to acquire this kinetic energy?
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a. east or west of the prime meridian. b. north or south of the prime meridian. c. north or south of the equator. d. north or south of the celestial equator.