a detailed understanding of the genesis of planets is one of the major goals for the astronomical community, equal in import to investigation of the origin of the universe as a whole. iras provided the first important step towards such an understanding with the discovery of resolved dust disks surrounding three nearby a stars (beta pic, fomalhaut and vega). models constructed to explain these data have concluded that the dust responsible for the infrared emission seen by iras is most plausibly produced by collisions of larger planetesimals, perhaps during an evolutionary phase similar to the era of maximum bombardment when the planets in our solar system were assembled, and thus that these disks are signatures of planet formation. the next critical steps in deepening our understanding would be to establish the fraction of stars which ultimately produce debris disks, and to infer the time history of planetesimal collisions from observations of the evolution of these disks. we propose a program aimed at achieving these goals from iso pht observations of a sample of about 60 a stars selected from four nearby open clusters spanning a range of ages from the epoch just following the end of the disk accretion phase (t virgul 5 - 10 myr) to an age comparable to that of vega and beta pic. we will measure the entire sample at 60 microns and do a subset of the stars in the two youngest clusters at 25, 60 and 100 microns. when combined with ground-based jhk and 10 micron photometry, these observations will allow us to measure the timescale for the inner disk clearing which is observed in the three prototype a stars. this program is complementary to the extant gto program because it samples stars in a critical age range: 5 < t < 30 myr.
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, 1999, Dust Around .A. Stars In Young Open Clusters Comma Part 1, 1.0, European Space Agency, https://doi.org/10.5270/esa-eash5gf
