Rossiter-McLaughlin effect
Encyclopedia
The Rossiter–McLaughlin effect is 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 or parent star. As the main star rotates on its axis, one quadrant of its photosphere
will be seen to be coming towards the viewer, and the other quadrant to be moving away. These motions produce blueshifts and redshift
s, respectively, in the star's spectrum, usually observed as a broadening of the 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. This 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. 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, strongly suggesting that dynamical interactions rather than planetary migration
produce these objects.
Astronomical spectroscopy
Astronomical spectroscopy is the technique of spectroscopy used in astronomy. The object of study is the spectrum of electromagnetic radiation, including visible light, which radiates from stars and other celestial objects...
phenomenon observed when either an eclipsing binary's secondary star or an extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
is seen to transit
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...
across the face of the primary or parent star. As the main star rotates on its axis, one quadrant of its photosphere
Photosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...
will be seen to be coming towards the viewer, and the other quadrant to be moving away. These motions produce blueshifts and redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
s, respectively, in the star's spectrum, usually observed as a broadening of the spectral line
Spectral line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies.- Types of line spectra :...
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. This 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. This effect has been used to show that as many as 25% of hot Jupiters
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
are orbiting in a retrograde direction with respect to their parent stars, strongly suggesting that dynamical interactions rather than planetary migration
Planetary migration
Planetary migration occurs when a planet or other stellar satellite interacts with a disk of gas or planetesimals, resulting in the alteration of the satellite's orbital parameters, especially its semi-major axis...
produce these objects.