Recessional velocity
The rate at which an astronomical object becomes more distant from an observer / From Wikipedia, the free encyclopedia
Recessional velocity is the rate at which an extragalactic astronomical object recedes (becomes more distant) from an observer as a result of the expansion of the universe.[1] It can be measured by observing the wavelength shifts of spectral lines emitted by the object, known as the object's cosmological redshift.
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