There is an opportunity in the coming decade to make fundamental advances in understanding the origins of stars and planets, and to ascertain the frequency of potentially habitable worlds. These compelling scientific opportunities have far-reaching implications in areas ranging from cosmic evolution and galaxy formation to the origins of life. The paths by which star-forming clouds produce stars and planet-forming disks have become much clearer over the past decade, and a startling diversity of planets orbiting nearby stars has been discovered. We now stand on the verge of determining whether habitable worlds are common in the galaxy. Moreover, there exists the immediate possibility of identifying any such worlds circling nearby very cool stars and of characterizing their physical properties and atmospheres as the search for signs of habitation is carried out. Now is the time to take advantage of this progress to answer some of the key questions of our cosmic origins that have inspired scientists and fascinated the public.
The Astro2010 Science Frontiers Panel on Planetary Systems and Star Formation was charged to consider science opportunities in the domain of planetary systems and star formation—including the perspectives of astrochemistry and exobiology—spanning studies of molecular clouds, protoplanetary and debris disks, and extrasolar planets, and the implications for such investigations that can be gained from ground-based studies of solar system bodies other than the Sun.1 The panel identifies four central questions that are ripe for answering and one area of unusual discovery potential, and it offers recommendations for implementing the technological advances that can speed us on our way. The questions and the area of unusual discovery potential are these:
How do stars form?
How do circumstellar disks evolve and form planetary systems?
How diverse are planetary systems?
Do habitable worlds exist around other stars, and can we identify the telltale signs of life on an exoplanet?
Discovery area: Identification and characterization of nearby habitable exoplanets.
The process of star formation spans enormous ranges of spatial scales and mass densities. The first stage involves the formation of dense structures that con-