Long-term spectral observations of a single star located in the constellation of Pisces showed that the wavelength of the hydrogen line Ha in its spectrum varies in the range from 656.42 nm to 656.55 nm with a period of 1 year. Explain the observed effect and determine the speed of this star relative to the Sun. The laboratory wavelength of the H line is 656.28 nm.
The observed fluctuations in the positions of lines in the spectrum of the star are associated with the orbital motion of the Earth. The constellation Pisces is zodiacal, therefore, the stars belonging to it are located near the plane of the Earth’s orbit and their relative velocities measured from the Earth’s surface experience oscillations with an amplitude of ± 30 km / s (the value of the Earth’s orbital velocity) relative to the star’s own radial velocity; about +94 km / s (the star moves away from the Sun).
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