At an astronomical conference, an astronomer gives a report on a star that interests astronomers because of hints that it may have a planet around it. In his report the astronomer gives the average speed with which this star is moving away from the Sun. How did the astronomer measure this speed?

Explanation:

The astronomer must have evaluated the Doppler shift in the lines of star's spectrum. The speed at which the star is moving away from the sun will cause in the shift in spectral lines emitted from the star. The shift in spectral line is not a change of whole pattern but a change is shade of color. It may get bluish or reddish in nature. So if the star moves away the spectral lines converge to a more reddish color. The degree of convergence is calibrated with respect to speed of light c = 3.0 * 10^8 m/s.

i think it’s a. this is because if they measured the mass of something with a mass of 150g, then their final answer would have to be approximately 150g. though all of their answers are almost 150, rosa and tran have the closest answers (or the exact answer) to the accurate one.

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