The highly accurate astrometric method involves observing the movement of a host star’s position in the sky as it orbits around the center of mass of the star-planet system. Knowing the mass of the star then allows the true mass of the planet, as well as its orbital parameters--including the semi-major axis, eccentricity, and inclination--to be determined. CAPSCam should yield astrometric accuracies of 0.25 millarcsec per epoch. This accuracy is sufficient to detect planets with masses as low as 1/10 the mass of Jupiter on 12-year orbits around nearby late M dwarf stars, with a signal-to-noise ratio of four.

Utilizing the CAPSCam, Boss, Weinberger and team plan to follow at least 100 nearby low-mass stars, particularly M, L, and T dwarfs for 10 years or more, in order to detect Jupiter-mass planets with orbital periods sufficiently long to permit the existence of habitable, Earth-like planets closer to the host star. Click here for more images of CapsCam.