CfA Colloquium Schedule Spring 2010
 11 February 2010

11 February 2010

Speaker: Bruce Macintosh (LLNL)

Title: Images and spectra of an extrasolar planetary system

Abstract: Although more than 400 extrasolar planets are now known, almost all have been detected indirectly - through radial velocity measurements or eclipses of their parent star. Direct detection - spatially resolving the planet from the star - opens up new areas of exoplanet phase space and new avenues for planet characterization. It is also extremely challenging, since a mature Jupiter-like planet is 10^9 times fainter than its host star. The promise of this approach was recently demonstrated with HST images of a planet orbiting Fomalhaut and adaptive optics images of a three-planet system orbiting the young A star HR8799. I will discuss the HR8799 system in detail, including photometry, properties of the host star, astrometry and orbital stability. We have also now obtained a spectrum of the outermost planet in the system - the coolest exoplanet ever studied spectroscopically - and these are showing an atmosphere very different from a brown dwarf. The HR8799 planets were detectable because they are extremely young (60 Myr) and massive (5-10 Jupiter masses.) To next major step in direct detection will be dedicated instruments such as the Gemini Planet Imager (GPI). GPI will use a 4000-actuator MEMS deformable mirror, an advanced coronagraph, and nanometer-precision wavefront sensing to achieve contrasts 1-2 orders of magnitude better than any current ground or space facility. I will briefly discuss the design and scientific capabilities of GPI, which is planned to have first light in 2011 on the Gemini South 8-m telescope.

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