R. Paul Butler develops precise stellar radial velocity measurements for detecting orbiting companions. With Geoffrey W. Marcy, he developed iodine-cell Doppler calibration, superimposing a dense reference spectrum on the same light entering a stellar spectrograph.
The reference lines constrain both the wavelength scale and the instrumental point spread function during the observation. Modeling them together with the shifted stellar radiation spectrum reduces errors caused by changes in the instrument. Their 1992 tests obtained a velocity scatter below over a year, providing a practical foundation for searches for low-mass companions.[ref]
Precision Radial Velocities with an Iodine Absorption Cell by Geoffrey W. Marcy and R. Paul Butler. p. 270, abstract; introduction on differing optical paths and systematic errors
Portrait of R. Paul Butler
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R. Paul Butler is a prominent figure in the field of astronomy, particularly known for his work in astrophysics and exoplanet research. He has contributed to the discovery and characterization of numerous exoplanets, often using radial velocity methods. Butler has published various scientific papers and collaborated with other researchers in the field. His work has been instrumental in advancing our understanding of planetary systems beyond our own. If you were referring to something else related to R. Paul Butler, please provide additional context!