Collaborative Research: Infrared RV Planet Search with Externally Dispersed Interferometry II: Optimization

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

One of the most effective means employed by astronomers to search for planets around stars other than our sun is to try to detect the velocity shift of the star as the planet moves about the star in its orbit. This well proven technique employs an instrument called a spectrograph to measure the small shifts in wavelength of features in a star's spectrum. The shifts are due to the familiar Doppler effect and are directly related to the changes in the star's velocity. But these velocity shifts are very small, and in order to measure them with great accuracy it is necessary to employ some scheme to calibrate the wavelength of the light in the spectrograph. One relatively new technique is to use interferometry, measuring the "interference" of two beams of light when they come together. At a particular wavelength, the two beams of light will cause fringes to appear which are spaced according to their wavelengths. By measuring the spacing of these fringes, wavelengths can be determined very accurately. Dr. Jerry Edelstein of the University of California-Berkeley and Dr. James Lloyd of Cornell University are applying this technique to a spectrograph that works not in visual light, but in the infrared. Infrared light is very useful in the study of cooler and smaller stars which are more numerous than hot stars. Finding planets around these stars will give us a much clearer picture than we currently have of how planets are actually formed and evolve. Since these stars are cooler than the massive hot stars that have been most frequently studied, their habitable zones, the region at the distance from the star where conditions may be suitable for life to begin, are much closer to the parent star. Most of the planets discovered so far have been "gas giants" like Jupiter and are located too far from their star for biology as we know it to exist. But with this new instrument, smaller earth-like planets may be detected in the habitable zone of cool stars. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.