Taking the Measure of Planets in the Globular Cluster 47 Tucanae
Hubble Space Telescope project GO-8267

    We propose a sensitive search for planetary companions in close orbits around upper main sequence stars in the 47 Tuc via transit signals from WFPC2 time-series photometry.  About fifty such systems will be detected with planetary radii errors of only 2-4% from the signal depth, and accurate periods from at least two transits.  Follow-up radial-velocity spectroscopy from the VLT and/or Gemini should provide velocity measurements for the best 25% of candidates to provide planetary masses (sin(i)~1 from transits).  Densities to ~15-20% 1-(sigma) errors will follow for planets with approximately Jovian mass and size providing for the first time meaningful, physical constraints on extra-solar-planet theory.

    Many other science applications will follow from these extensive observations, e.g. U, V, I imaging well down the White Dwarf cooling sequence in the cluster core, bottom of main sequence definition to M_V ~13.8, M_I ~12.8, and a definitive survey for eclipsing binaries.

    We propose this as a major survey program that will result in a unique and valuable addition to the HST archive. Albeit "scientifically risky" in that planets are not yet known to exist in globular clusters, there is little technical risk - HST is uniquely capable of providing the requisite, high-dynamic range, time series photometry.