Astrophysics (Index)About

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).

A bit of a rotating star's light is red- or blue-shifted, given some is coming from surface rotating toward us and some from the other side, rotating away from us. A transit blocks part of the starlight, the relative amounts of shifted light in our view depending upon which portion of the transit is in progress. The order of which shift dominates first during the transit reveals whether the orbit is prograde or retrograde, "blue shift first" indicating a retrograde orbit.

(exoplanets,binary stars,redshift,spectrography,transits)
Further reading:

Referenced by pages:
eclipse mapping