An Etymological Dictionary of Astronomy and Astrophysics

A → spectroscopic phenomenon observed when either an → eclipsing binary’s → secondary star or an → extrasolar planet is seen to
→ transit across the face of the → primary body. Because of the rotation of the star, an asymmetric distortion takes place in the → line profiles of the stellar spectrum, which changes during the transit. The measurement of this effect can be used to derive the → alignment of the → orbit of the transiting exoplanet with respect to the → rotation axis of the star.

See also: Named after Richard Alfred Rossiter (1886-1977) and Dean Benjamin McLaughlin (1901-1965), American astronomers.