What year was the phenomenon used to explain the color of binary stars described?
Doppler effect The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave for an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
Zeta Capricorni Zeta Capricorni, (ζ Cap, ζ Capricorni), is a fourth-magnitude star in the constellation Capricornus. ζ Capricorni is a binary star, with the primary component ζ Capricorni A being a yellow G-type giant with an apparent magnitude of +3.77. It is considered one of the prototypical examples of a Barium star, properties of which include overabundances of carbon molecules (such as C) and s-process elements. Zeta Capricorni has an overabundance of the s-process element praseodymium.