Doppler spectroscopy
Doppler spectroscopy is an indirect detection method that measures the velocity shift and result stellar spectrum shift associated with an orbiting planet. This method is also known as the Radial Velocity method. It is most successful for main sequence stars The spectra of exoplanets have been successfully partially retrieved for several cases, including HD 189733 b and HD 209458 b. The quality of the retrieved spectra is significantly more affected by noise than the stellar spectrum. As a result, the spectral resolution, and number of retrieved spectral features, is much lower than the level required to perform doppler spectroscopy of the exoplanet.