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A. P. Boss (DTM/CIW)
The extrasolar giant planets discovered by indirect detection have all been found in orbit around stars with ages comparable to the sun. In order to determine the mechanism of giant planet formation, it may be necessary to find the epoch of giant planet formation by searching for giant planets around a sample of very young stars. The core accretion mechanism for giant planet formation requires at least 1 Myr to form a Jupiter-mass planet, whereas the disk instability mechanism can form a multi-Jupiter-mass protoplanet around even the youngest (0.1 to 1 Myr) stars. Recently S. Terebey used HST to take what may be the first image of an extrasolar giant planet. Terebey found evidence for a 2 to 3 Jupiter-mass planet (TMR-1C) being ejected from a binary protostar system with a separation of 40 AU. Because the age of TMR-1C is estimated to be around 0.1 Myr, if TMR-1C is a giant planet, it must have formed by disk instability. L. Rodriguez has used the VLA to image disks around the L1551 IRS-5 binary protostars that might form giant planets susceptible to ejection. The disks have radii of 10 AU and masses of 0.03 and 0.06 solar masses, while the binary has a separation of 45 AU. In order to learn whether such a binary companion can help induce the formation of giant planets by disk instability, 3D hydrodynamical models of disks with 0.04 solar masses inside 10 AU were evolved in time, subject to the gravity of a binary star companion on a circular orbit at 40 AU distance. In the absence of the binary companion, the disk is stable, but in the presence of the binary companion the disk forms a multi-Jupiter-mass protoplanet in 0.002 Myr.