Oct 10, 2007 7:30pm - Planetary Debris Disk Observations with the Keck and Hubble Telescopes - Dr. James Graham, Herzberg Institute/UC Berkeley

In our own solar system primitive bodies, such as comets and asteroids release trails of debris, seeding interplanetary space with tiny dust grains. Born within the plane of the solar system, trillions of dust grains form a tenuous, flattened cloud called a circumstellar disk. If gravity were the only force acting on these grains, then they would, like the planets, orbit the Sun forever.

Various small but persistent influences, including radiation pressure from Sun light and drag forces, either cause grains to spiral inward to the Sun or blow them out to interstellar space. However, this zodiacal dust is persistent because asteroids and comets continue to replenish the disk with fresh debris. From our perspective on Earth, this dust is visible as the faint band of zodiacal light or the "false dawn". This is sunlight reflected from transitory dust in the plane of the solar system.

About 15% of nearby solar-type stars are now known to have similar dusty disks that are assumed to be similarly replenished by the disruption larger bodies. I will discuss recent imaging of these exo- planetary debris disks with Hubble and the Keck telescopes, and their implications for the formation of planets.

Presentation - 2Mb pdf

Bio
James R. Graham is a professor of astronomy at the University of California, Berkeley, where he is project scientist for the Gemini Planet Imager project---an "extreme" adaptive optics system designed to allow direct detection of exoplanets. Previously, Graham was a senior research fellow at the California Institute of Technology, Pasadena. His PhD is from Imperial College, University of London. Graham is currently on sabbatical leave from Berkeley at HIA/DAO in Victoria.