Detection of Close-In Extrasolar Giant Planets Using the Fourier-Kelvin Stellar Interferometer

We evaluate the direct detection of extrasolar giant planets with atwo-aperture nulling infrared interferometer, working at angles${\theta}<{\lambda}/2B$, and using a new `ratio-of-two-wavelengths' technique.Simple arguments suggest that interferometric detection and characterizationshould be quite possible for planets much closer than the conventional innerworking angle, or angular resolution limit. We show that the peak signal from anulling infrared interferometer of baseline ($\lesssim 40$ meters) will oftenoccur `inside the null', and that the signal variations from path-differencefluctuations will cancel to first order in the ratio of two wavelengths. Usinga new interferometer simulation code, we evaluate the detectability of all theknown extrasolar planets as observed using this two-color method with theproposed {\it Fourier Kelvin Stellar Interferometer (FKSI)}. In its minimumconfiguration {\it FKSI} uses two 0.5-meter apertures on a 12.5-meter baseline,and a $\pm 20^{\circ}$ field-of-regard. We predict that $\sim 7$ knownextrasolar planets are directly detectable using {\it FKSI}, withlow-resolution spectroscopy ($R \sim 20$) being possible in the most favorablecases. Spaceborne direct detection of extrasolar giant planets is possible with$\sim 12$ meter baselines, and does not require the much longer baselinesprovided by formation flying.Comment: Accepted for publication in ApJ Letter