View source for Astronomy:Rossiter–McLaughlin effect

{{Short description|Spectroscopic phenomenon in astronomy}}
[[File:Animation of the Rossiter-Mclaughlin (RM) effect.gif|thumb|Animation of the Rossiter-Mclaughlin (RM) effect]]
The '''Rossiter–McLaughlin effect''' is a spectroscopic phenomenon observed when an object moves across the face of a star.

==Description==

The Rossiter–McLaughlin effect is a [[Physics:Astronomical spectroscopy|spectroscopic]] phenomenon observed when either an [[Astronomy:Eclipsing binary|eclipsing binary]]'s secondary star or an extrasolar planet is seen to [[Astronomy:Astronomical transit|transit]] across the face of the primary or parent star.

As the main star rotates on its axis, one quadrant of its [[Astronomy:Photosphere|photosphere]] will be seen to be coming towards the viewer, and the other visible quadrant to be moving away. These motions produce [[Astronomy:Blueshift|blueshift]]s and [[Astronomy:Redshift|redshift]]s, respectively, in the star's spectrum, usually observed as a broadening of the [[Physics:Spectral line|spectral line]]s. When the secondary star or planet transits the primary, it blocks part of the latter's disc, preventing some of the shifted light from reaching the observer. That causes the observed mean redshift of the primary star as a whole to vary from its normal value. As the transiting object moves across to the other side of the star's disc, the redshift anomaly will switch from being negative to being positive, or vice versa.

[[Image:Rossiter-McLaughlin effect.svg|frame|center|The viewer is situated at the bottom. Light from the anticlockwise-rotating star is blue-shifted on the approaching side, and red-shifted on the receding side. As the planet passes in front of the star it sequentially blocks blue- and red-shifted light, causing the star's apparent radial velocity to change, but it does not in fact change.]]

==Retrograde Motion of Hot Jupiters==
This effect has been used to show that as many as 25% of hot Jupiters are orbiting in a retrograde direction with respect to their parent stars,<ref name="Triaud2010"/> strongly suggesting that dynamical interactions rather than [[Astronomy:Planetary migration|planetary migration]] produce these objects.

== History ==
J. R. Holt in 1893 proposed a method to measure the [[Astronomy:Stellar rotation|stellar rotation]] of stars by using [[Astronomy:Radial velocity|radial velocity]] measurements. He predicted that when one star of an eclipsing binary eclipsed the other, it would first cover the advancing blueshifted half and then the receding redshifted half. That motion would create a [[Astronomy:Redshift|redshift]] of the eclipsed star's spectrum followed by a [[Astronomy:Blueshift|blueshift]], which would thus appear as a change in the measured radial velocity in addition to that caused by the orbital motion of the eclipsed star.<ref name="Triaud2013"/>

The effect is named after Richard Alfred Rossiter and Dean Benjamin McLaughlin.

== Further reading ==
*{{Cite journal |first1=Y. |last1=Ohta |author-link2=Atsushi Taruya |first2=A. |last2=Taruya |name-list-style=amp |author-link3=Yasushi Suto |first3=Y. |last3=Suto |title=The Rossiter–McLaughlin Effect and Analytic Radial Velocity Curves for Transiting Extrasolar Planetary Systems |journal=The Astrophysical Journal |volume=622 |issue=1 |year=2005 |pages=1118–1135 |doi=10.1086/428344 |arxiv=astro-ph/0410499 |bibcode=2005ApJ...622.1118O|s2cid=10420706 }}
*{{Cite journal |first=D. |last=Anderson |display-authors=0 |year=2010 |title=WASP-17b: An Ultra-Low Density Planet In A Probable Retrograde Orbit |journal=The Astrophysical Journal |volume=709 |issue=1 |pages=159–167 |doi=10.1088/0004-637X/709/1/159|arxiv=0908.1553 |bibcode = 2010ApJ...709..159A |s2cid=53628741 }}
*{{Cite book | first = J. |last=Winn |year=2006| chapter= Exoplanets and the Rossiter-McLaughlin Effect |series=ASP Conference Proceedings |title=Transiting Extrasolar Planets Workshop | volume = 366 | page = 170 |editor1=C. Afonso |editor2=D. Weldrake |editor3=T. Henning |arxiv = astro-ph/0612744|bibcode = 2007ASPC..366..170W }}

==References==
{{Reflist|refs=

<ref name="Triaud2010">{{cite journal |last=Triaud |first=A. H. M. J. |display-authors=0 |year=2010 |title=Spin-orbit angle measurements for six southern transiting planets: New insights into the dynamical origins of hot Jupiters |journal=Astronomy & Astrophysics |volume=524 |pages=A25 |doi=10.1051/0004-6361/201014525 |arxiv=1008.2353 |bibcode = 2010A&A...524A..25T |s2cid=59320239 }}</ref>

<ref name="Triaud2013">{{cite journal | title=The EBLM project I. Physical and orbital parameters, including spin-orbit angles, of two low-mass eclipsing binaries on opposite sides of the brown dwarf limit | last1=Triaud | first1=A. H. M. J. | last2=Hebb | first2=L. | last3=Anderson | first3=D. R. | last4=Cargile | first4=P. | last5=Cameron | first5=A. Collier | last6=Doyle | first6=A. P. | last7=Faedi | first7=F. | last8=Gillon | first8=M. | last9=Gomez Maqueo Chew | first9=Y. | display-authors=1 | journal=Astronomy and Astrophysics | volume=549 | at=A18 | year=2013 | arxiv=1208.4940 | bibcode=2013A&A...549A..18T | doi=10.1051/0004-6361/201219643 | s2cid=54529197 | url=http://orbi.ulg.ac.be/jspui/handle/2268/135087 }}</ref>

}}

==External links==

{{DEFAULTSORT:Rossiter-McLaughlin effect}}
[[Category:Planetary science]]
[[Category:Astronomical spectroscopy]]
[[Category:Doppler effects]]

{{Sourceattribution|Rossiter–McLaughlin effect}}