Christopher Stark
Physics Ph.D. Student

I'm interested in all things exoplanets, but my research focuses on debris disks and disk-planet interactions. I developed and currently maintain the Exozodi Simulation Catalog, which catalogs the resonant debris disk structures we may resolve with future exo-Earth-imaging missions. Here's what else I'm currently working on...

Collisional Debris Disks
I have created a "collisional grooming" algorithm that will allow for the self-consistent and simultaneous treatment of resonant gravitational dynamics and grain-grain collisions in debris disks for the first time. Check out the paper that describes how this algorithm works here.

This should allow us to accurately model disks like that around Fomalhaut, and create models that can be directly compared with observations. At right is a preliminary model of the collisional Fomalhaut disk (publication to come soon!). Shown is a synthesized 500 nm image for a model of 200 micron grains with a Henyey-Greenstein scattering phase function with g=0.2.

Exozodiacal Cloud Structure
I am modeling the circumstellar ring structures that Earth-like planets can create in dusty disks around other stars. The dust in these disks is short-lived, and must be replenished by collisions or outgassing of parent body planetesimals. After being launched from their parent bodies, the dust particles lose angular momentum due to Poynting-Robertson (PR) drag and spiral inward toward their host star. Along the way, they can get trapped in mean-motion resonances with the planet where they stay until they are eventually ejected due to close encounters with the planet. The temporary trapping of particles in mean motion resonances creates a large circumstellar ring structure like those shown below.

I have developed a hybrid symplectic integrator for our models and implemented it on the Discover cluster at NASA GSFC. Check out my catalog of debris disk ring structures due to terrestrial-mass planets. A few examples of my simulations are shown below.

      Face-on cloud                 Inclined cloud                 Edge-on cloud                 Face-on cloud
     2 M_Earth planet               1 M_Earth planet                1 M_Earth planet           Jupiter-mass planet

Observations of Debris Disks
I am part of a team observing debris disks with the Keck Interferometer Nuller. We're looking for signs of dust near the habitable zones of other stars, similar to our zodiacal cloud, but much brighter. Check out a couple of recent press releases (here and here) on our observations of 51 Ophiuchi.

dustmap.pro
All of the above images were synthesized using dustmap.pro, an IDL package I wrote to view debris disks from any vantage point--even from within!  dustmap.pro produces 2D or 3D density histograms and can synthesize images of dust clouds illuminated by starlight, including both scattered light and thermal emission.  It uses scattering and absorption coefficients from Mie theory for astronomical silicate dust and a modified Hong phase function.  You can use it too--all you need is a set of discrete 3D positions for input.  Download v2.0 of dustmap.pro here. 

***UPDATE: dustmap.pro has been updated to v2.0. Several new functions have been added, the default imaging mode has been changed from the 3D mode to the 2D mode, and two sample input files have been included with the distribution. See the README.txt file for more information.

To install dustmap.pro, access the directory where you saved the .tgz file and type

tar xvzf dustmap.2.0.tgz

Then check out the README.txt file.  Please let me know if you run across any bugs.

dustmap.pro also works in conjunction with ZODIPIC, which you can find on Marc Kuchner's home page.

Recent Refereed Publications:

• Defrere, D., Absil, O., den Hartog, R., Hanot, C., & Stark, C., "Nulling Interferometry: Impact of Exozodiacal Clouds on the Performance of Future Life-Finding Space Missions," A&A, accepted. [Preprint]
• Stark, C. C. & Kuchner, M. J., "A New Algorithm for Self-Consistent 3-D Modeling of Collisions in Dusty Debris Disks," ApJ, in press. [Preprint]
• Stark, C. C., Kuchner, M. J., Traub, W. A., Monnier, J. D., Serabyn, E., Colavita, M., Koresko, C., Mennesson, B., & Keller, L. D., "51 Ophiuchus: A Possible Beta Pictoris Analog Measured with the Keck Interferometer Nuller," ApJ 703, 1188 (2009). [Preprint]
• Stark, C. C. & Kuchner, M. J., "The Detectability of Exo-Earths and Super-Earths Via Resonant Signatures in Exozodiacal Clouds," ApJ 686, 637 (2008). [Preprint]

Recent Presentations:

• "Modeling the Fomalhaut Debris Disk Structure with a Collisional Grooming Algorithm," AAS DPS Meeting (10/8/09)  PPT
• "Collisional Grooming: Implementing Collisions After N-body Integrations," ISSI, Bern, Switzerland (4/8/09)  PPT
• "Debris Disk Modeling: From Exozodiacal Structures to Collisional Disks," STScI (1/26/09)  PPT
• "Keck Interferometer Nuller Observations of the 51 Ophiuchi Circumstellar Disk," AAS Meeting (1/7/09)  PPT
• "Debris Disks -- Theory and Modeling," Exoplanet Forum, Pasadena, CA (5/30/08)  PPT