Suppose that the physical properties of two stars are identical in every way --- for example, same distance, same mass, same tem
perature, same chemical composition, and same speed relative to Earth --- except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?
By measuring it's Radical velocity using Doppler Phenomenon...
Explanation:
It is done by measuring the absorption spectrum produces by a star as a result of measuring Doppler's relative wavelength. The star with the lower speed must have lower absorption spectrum extent as compared to the faster one.
