Institute for Advanced Study Informal Astrophysics Seminar

Four centuries ago the son of an Italian lutenist constructed the telescopes with which he would observe the Solar System and forever alter humanity's perception of its place in the Cosmos. Today, that perspective continues to change with the discovery of numerous planets around other Sun-like stars, primarily using the Doppler radial velocity and transit methods. There are numerous surveys to find more planets and I will describe one - ARCHIPELAGO - which is searching the nearest, low mass stars for planets with masses intermediate that of Earth and Neptune. We are screening a new catalog of more than 10,000 late K and early M star candidates within 50 parsecs to verify main sequence status, determine spectral type, estimate heavy element abundance, and assay chromosphere emission. We will identify planet-hosting stars using a multi-stage, hybrid RV-transit scheme that is designed to efficiently detect planets whose mass and radius can both be measured. Among these planets may be some that are very unlike the members of our Solar System. One hypothetical class of planet is composed principally of water, i.e., high-pressure phases of ice underlying a steam atmosphere or liquid ocean. Another will be composed almost entirely of iron; a third may have a mantle of carbides rather than silicates. None may be suitable for life as we know it; all will test theories of planet formation and inform conjecture about the frequency of Earth-like planets and life in the Cosmos.