I am an Adjunct Professor in the Astronomy Department at the University of California, Berkeley.

My expertise is in providing direct images of planetary systems around nearby stars. I use some of the world's most advanced observatories, such as the Hubble Space Telescope, Keck Observatory, the Gemini Telescopes, and ALMA. One remarkable image is the planetary system surrounding Fomalhaut (see below), which is a bright star located 25 light years away in the constellation Pisces Australis. Though direct images are difficult to obtain and currently quite rare, they provide unique and fundamental information about exoplanetary systems, such as:

  • The masses of exoplanets, by analyzing how bright they appear and how stable their orbits should be assuming different properties.
  • Their composition, by analyzing the color of thermal emission from the planet, or by obtaining a spectrum.
  • The origin of exoplanets, by comparing their current observed properties with simulations of how planets form in a circumstellar disk and subsequently evolve.

Ultimately, these data will give us an empirical notion of how common or rare our own planetary system must be in our own galaxy and throughout the universe.

NEWS (Dec. 2, 2015): Press Release announcing our discovery of a disrupted planetary system -- the "exiled exoplanet" - using the Gemini Planet Imager and the Hubble Space Telescope.

NEWS: ALMA reveals structure of the HL Tau protoplanetary disk.

For images concerning Fomalhaut b, the recent visible light detection of an exoplanet candidate orbiting the bright star Fomalhaut, please see the NASA and Space Telescope Science Institute press releases:

For the publicly accessible manuscripts related to these discoveries from our group:

I have also posted some of my dynamical studies on YouTube (click on image).


December 2013 Update: Fomalhaut is a triple star system. Fomalhaut A is the massive star shown above that has the well-known comet belt and planet Fomalhaut b (you could call the planet Fomalhaut Ab). Fomalhaut B is a less massive star more like the Sun, and Fomalhaut C is a red dwarf. Planets have yet to be discovered around the two sister stars Fomalhaut B and C, but the news is that a belt of comets has just been discovered around Fomalhaut C using infrared observations made by the Herschel observatory. The same observatory did not find a belt of comets around Fomalhaut B, therefore introducing the mystery of why the most massive and least massive stars in the system should have comet belts, and not the star in the middle. Below is my illustration of the system.

Click here to read the Royal Astronomical Society press release. The lead investigator is Grant Kennedy at the University of Cambridge.

March 9, 2014 Popular Press Update: The ALMA/Hubble hybrid image of Fomalhaut was shown as an enormous background to 60 Minutes correspondant Bob Simon. In the foreground is astronomer Eduardo Hardy. "60 Minutes" is one of the most widely watched news programs in the United States.

We are commissioning the Gemini Planet Imager beginning November 2013. GPI is an advanced adaptive optics system and coronagraph designed to directly detect warm planets and debris belts surrounding young stars such as Beta Pictoris and Fomalhaut. We expect that by 2014 various GPI science projects will discover and characterize 10x more exoplanets via direct imaging and spectroscopy than existed in 2011. Please see the GPI website for more info. This project has been ten years in the making, and I currently serve on the GPI Science Steering Committee and the Debris Disk Science Team. Here is the press release from Gemini Observatory: http://www.gemini.edu/node/12113

Why is GPI a genuine game-changing astronomical instrument? During commissioning, the exoplanet Beta Pic b was easily seen in 60 second exposures with no processing of the data. Previously, this was impossible unless the observatory spent hours observing the star and the astronomers applied special techniques to process the data. The same is true for GPI observations of the HR 4796A comet belt - it was visible immediately by eye on the screen.

Below is the GPI image of a dusty comet belt surrounding the bright star HR 4796A. On the left is a single image snapshot, on the right is a fully processed image showing how the dust polarizes starlight. You can see previous images of this comet belt in the image gallery of my Circumstellar Disk Learning Site.

In 2007 I founded the Spirit of Lyot conferences. The fundamental motivation is to nurture a balance between scientific talent and experimental innovation that is personified by the career of the famous French astronomer Bernard Lyot, inventor of the solar coronagraph.

In 2010 our colleagues in France hosted the second Spirit of Lyot conference in Paris, with a 50 percent increase in attendance.

In 2014 we announced the third Lyot conference to take place June, 2015, in Montreal, Canada, under the local leadership of Rene Doyon and David Lafreniere (Universite de Montreal).