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