Dr. Marcy will search for extremely low mass, dark companions to stars by using the reflex velocity of the host star. He will use a new measurement technique which should significantly improve the precision of radial velocities and permit the detection of stellar companions with masses as low 3 Jupiter-masses, for orbital periods up to the duration of the observations. He hopes to further improve the analysis so that companions of even lower mass will be detectable. A long standing difficulty in astronomy as been the determination of the properties of substellar objects, "stars" of too little mass to support stable nuclear hydrogen burning. Such objects bear on several diverse subfields of astronomy, such as: (1) the identification of unseen matter both in the disk of our Galaxy and in halos of other galaxies; (2) the understanding of star formation and protostellar fragmentation at low stellar masses; and (3) the determination of masses of low mass stars orbited by substellar companions to better determine the stellar mass function and the frequency of binary stars at the low mass end of the main sequence of stars. Although there are several interesting candidates, there are currently no confirmed bona fide substellar objects known outside our Solar System. Dr. Marcy's objective is to use an improved observational technique that will permit detection of substellar companions of stars down to masses of about 1 Jupiter- mass. This award is made under the auspices of the NSF Research in Undergraduate Institutions (RUI) program.
