A major problem in stellar astrophysics has been reconciling the discovery that at least one half of the mature (main sequence) stars one sees in the skies are actually close double stars, or "binary" stars, whereas stars that are still forming, T Tauri stars, seem overwhelmingly to be single stars. Thanks largely to previous NSF-supported work by this Principal Investigator (PI) this discreprancy now seems clearly due to the difficulty of discovering binarity among very young stars from conventional spectroscopic techniques. Working at infrared wavelengths, the PI has used the moon as a "knife edge" to occult (eclipse) pre-main sequence stars in the Taurus region of the sky to determine whether they are single or double stars. In the last few years he has found that 13/28 of occulted T Tauri stars are members of double or triple star systems. The PI proposes to extend this work to T Tauri stars in the Ophiuchus region of the sky as the Moon's orbit progresses southward over the next few years. In addition to adding to the statistics of young binary stars, the PI plans to observe some of the occultation events from two locations simultaneously, Hawaii and Kitt Peak. This work is expected to clarify the conditions under which solar-type stars form binary stars as opposed to single stars with planetary systems.
