Michelson Postdoctoral Fellowship Recipients

2007 Postdoctoral Fellows

Daniel Fabrycky
Harvard-Smithsonian Center for Astrophysics

Dynamical Detection And Migration Of Multiple-Body Planetary Systems

With the discovery of planets orbiting other stars came numerous examples of multiple body systems: as of October 2006, 20 stars are known to host multiple planets and 31 planet-hosting stars are known to have at least one stellar companion. In our own planetary system, the planets only slightly perturb each other's orbits because of their relatively small eccentricities and inclinations and their generous spacing. The planets of other stars, in contrast, generally have a strong dynamical coupling to one another. If one of the planets transits the host star, transit-timing measurements will exquisitely constrain the system’s parameters and may even permit the detection of additional planets. I will develop a theoretical and statistical framework to diagnose the dynamical state of planetary systems by such measurements. The long-term perturbation of a planet by a companion star can drive its orbit to high eccentricity; with the help of tidal dissipation the planet may migrate to become a hot Jupiter. I will make theoretical models of such evolution to constrain the histories of planets in binaries on the basis of their orbits observable by Navigator observatories SIM and TPF.

Dan is currently an Assistant Professor at the University of Chicago.

Michael Fitzgerald
Lawrence Livermore National Laboratory

Architectures of Planetary Systems at High Contrast

Circumstellar disks are ideal places to search for signs of planets and their formation. The grains in debris disks are generated through the attrition and evaporation of primitive planet-building material. Their scattered light is only seen at high contrast, and the advancement of corona graphic techniques promises to greatly increase the number of resolved systems. I seek to maximize the sensitivity of diffraction-limited adaptive optics coronagraphy to both planets and debris disks by implementing a true roll deconvolution scheme. I will use the statistics and structure of speckles to facilitate the sifting of stellar point spread functions from circumstellar emission. I will carry out an observing campaign to resolve the disks, reveal their architectures, probe grain sizes and composition, and potentially detect young, self-luminous jupiters. Coupled with the advance in data processing, these observations are sensitive to indirect signatures of planets. Moreover, they trace the locations and evolution of primitive solid material. These advances in high-contrast technique will have direct application to instruments and missions currently in development. Understanding the diversity of debris disk architectures promises to uncover the mechanisms governing planet formation and disk evolution.

Michael is currently an Assistant Professor at the UCLA.

Andrea Isella
California Institute of Technology

Planet Formation In Pre-Main Sequence Disks

As a research project at Caltech/MSC I propose a multi-scale study of circumstellar disks based on Keck and CARMA interferometric observations of pre-main sequence stars. The aim of the project is to understand where and when planet formation take place and how this process modifies the structure of circumstellar disks. Infrared and millimeter observations will allow to characterize the disk structure at all distances from the central star, from the dust evaporation radius, at fraction of AU, until the disk outer radius, at hundreds of AUs. The data analysis, performed in the framework of the disk models developed during my Ph.D., will allow to determine physical properties of the circumstellar material (i.e., disk mass, gas and dust radial distribution and temperature, dust size and composition, gas cinematic), with the aim of investigating the dynamical perturbations driven by forming planets on the surrounding dust and gas. The proposed combination of Keck and VLTI observations will allow a fundamental improvement of the uv-plane coverage, bringing to a real breakthrough in our knowledge of pre-main sequence disks.

Andrea is currently an Assistant Professor at the Rice University.

Hannah Jang-Condell
Goddard Space Flight Center

Three-Dimensional Radiative Transfer in Disks with Planets

I propose to apply three-dimensional radiative transfer modeling to various types of disk-planet interactions, determining observable consequences as well as implications for planet formation theory. One application is to determine observable signatures of both disk instability and core accretion, to help settle to debate over which mechanism gives rise to giant planets. A second application is to model inner holes and gaps in disks to interpret resolved images of disk structure as well as to determine how the holes and gaps might form. A third application is to determine how much slowing of Type I migration of planets occurs from temperature perturbations caused by shadowing in the disk. I also hope to improve the modeling of dust properties in my disk calculations and address the freezing out of volatiles in shadows created by planets. I will work with researchers at both University of Maryland and NASA-Goddard Space Flight Center in my work.

Hannah is currently an Assistant Professor at the University of Wyoming.