2. how do doppler shifts of bipolar flows confirm that they lare moving away from a central object?

a. astronomers observe that the spectra is red shifted.
b. astronomers do not observe doppler shifts at all.
c. astronomers observe that the soectra is blue shifted.
d. astronomers observe both red and blue shifts in the spectra.

a. astronomers observe that the spectra is red shifted.

Explanation:

Doppler shift equation is related to the Doppler effect and refers to the change in a wave perceived frequency (or wavelength=color in the case of electromagnetic waves) when the emitter of the waves, and the observer move relative to each other.

From there, it is deduced that the farther the object is, the more redshifted it is in its spectrum. For example, as a star moves away from the Earth, its espectrum turns towards the red and as the star moves toward the Earth, its  espectrum turns towards the blue.

It should be noted that this effect bears its name in honor of the Austrian physicist Christian Andreas Doppler, who in 1842 proposed the existence of this effect for the case of light in the stars.