For finding the distances to globular clusters, Harlow Shapley used
A) RR Lyrae variables.
B) planetary nebulae.
C) eclipsing binaries.
D) Population I classical Cepheids.
E) Type I supernovae.
A
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You are studying a mystery companion to an evolved star, with mass transfer happening. Which of the following properties suggests that the companion is definitely a black hole?
A) The mystery companion has a mass of over 1.4 solar masses. B) The mystery companion has a mass of over 3 solar masses. C) The mystery companion has an X-ray emitting accretion disk. D) The mystery companion gives off periodic X-ray bursts.
The temperature of an object from which no heat energy can be extracted is
a. 0? F b. 0? C c. 0? K d. 100? K e. 100? C
You observe a rocket moving toward you. Compared to its length when it was at rest on the ground, you will measure its length to be:
1.shorter. 2.longer. 3.the same.
Our Sun's spectral temperature type is classified as a(n) ____ on the spectral sequence
a. O star b. F star c. G star d. K star e. M star