How do astronomers measure the temperature of stars?
A. The inverse square law is used.
B. By comparing the star's absolute and apparent brightness.
C. The rate of change of the color of the star is measured.
D. By looking at which absorption lines are present in the star's spectrum.
E. Temperature is determined from the radius of the star that is measured by radar.
Answer: D. By looking at which absorption lines are present in the star's spectrum.
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If vector = -3.0 - 4.0 , and vector = +3.0 -8.0 , then the magnitude of vector = - is
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