The radial velocity of a star, denoted vr, is its velocity along the line of sight of an observer. It is calculated from the Doppler shift in the lines of stellar spectra, taking into account the nature of the star. By comparing the observed spectra of a star with reference spectra we can measure the wavelength shift of the reference lines and thus determine vr.

A star receding from us has a redshifted spectrum and a positive radial velocity, while a star coming towards us has a blueshifted spectrum and a negative radial velocity.

Radial velocity is a measurement of how many radians per second that a signal travels. If we look at a sine or cosine wave as a rotating vector, the radial velocity is the angular speed of the vector. Radial velocity is represented by the small greek letter omega (ω). Radial velocity can be calculated from frequency using the formula:

ω = 2πf

Where f is the frequency of the waveform.

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