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Project Progress

Last year, UCLA astronomers Benjamin Zuckerman and Inseok Song announced the discovery of a brand new target for extrasolar planet hunters?the Beta Pictoris moving group (Zuckerman et al., 2001). These very near (~100 light years away) and very young (~12 million-year-old) stars are siblings of Beta Pic, ?the most famous dust-shrouded star in the sky? (Irion, 2001). This year, the catalog of youngest, nearest stars has been significantly expanded to ~200 members as a result of ongoing observations of the southern skies at the Siding Springs Observatory, eastern Australia, and at the Lick Observatory, University of California, Santa Cruz. Many of these very young stars are expected to have warm, Jupiter-class planets that should be visible in the thermal infrared (IR) using current NASA technology such as the Hubble Space Telescope.

Nearby stars that are surrounded by ?dust? show an infrared excess in the spectrum of their starlight. This is because the ?dust? is warmed by the star and re-emits energy at infrared wavelengths. Chen and Jura (2001) observed that the infrared excess from the nearby star Zeta Leporis is produced within six astronomical units of the star. This result strongly suggested the existence of a circumstellar belt of asteroids, the first one so far found outside our solar system. Although this study was not funded by the NAI, it raised the possibility of future collaboration, now under way, between astronomers and cosmochemists. Their combined approach will be to use the early solar nebula as an experimental model for young stellar objects and their dusty circumstellar disks (Zuckerman, 2001).

Astronomers Andrea Ghez and Caer McCabe have studied GG Tau, a young low mass star surrounded by a massive circumbinary ring, for evidence of dust grain growth beyond that of the interstellar medium (McCabe et al., 2002). Modeling shows that data obtained with the Hubble Space Telescope can be approximated by interstellar dust rather than primordial planet-forming material. This means that a better understanding of GG Tau?s role in the planet building process will require longer wavelength studies of scattered light and a better knowledge of the starting material for stellar system construction.