  How do planets form from circumstellar disks of gas and dust? What physical
processes are responsible for determining the final masses of forming stars and
ultimately the initial mass function (IMF)? The Hubble Space Telescope has made
major contributions in helping to address these fundamental questions. In the
next decade, the Space Infrared Telescope Facility (SIRTF) and the Next
Generation Space Telescope (NGST) will build on this heritage in the near- to
far-infrared. However several crucial questions will remain. We review recent
progress made in star and planet formation with HST, summarize key science
objectives for SIRTF and NGST, and suggest problems that would be uniquely
suited to a large aperture UV/optical space-based telescope. We focus on
studies that take advantage of high spatial resolution and the unique
wavelength range not accessible from the ground such as: 1) circumstellar disk
structure and composition (resolved images of dust and UV spectroscopy of gas);
and 2) extreme populations of young stars in the local group (UV imaging and
spectroscopy of massive star-forming regions). An 8m UV/O space telescope
operating from 1100-6000 Angstroms over fields of view 4-10' and with
spectroscopic capabilities from R = 3,000-10,000 down to < 1000 Angstroms would
be a powerful tool for star and planet formation research.
