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Rossiter-McLaughlin effect

(RM effect, RM)
(effect of transit on visible spectrum of the star)

The Rossiter-McLaughlin effect (RM effect, or just RM) is a spectroscopic effect on stars during transits, that reveals whether the transiting object (extra-solar planet or binary-star companion) has a retrograde orbit (i.e., opposite to the star's own rotation).

It is due to the hiding of some of the relatively red- or blue-shifted light from a rotating star by the transiting object, leaving more of the opposite-shifted light. Depending on which comes first during the transit reveals whether the orbit is retrograde, "blue shift first" indicating a retrograde orbit.

(exoplanets,binary stars,redshift,spectrography,transits)

Referenced by:
eclipse mapping