Decoding the Signatures of Exoplanets in Debris Disks
Exoplanets gravitationally interact with their environment, stirring up planetesimals and dust grains. These interactions can create large-scale structure in debris disks, in the form of clumpy circumstellar rings of material. The shape of these rings can tell us about the mass of the planet, its orbital parameters, the characteristics of the dust grains, the distribution of planetesimals, and the history of the planetary system. We can even use these structures as a means of indirectly detecting exoplanets when the planet itself is too dim to image.
Teasing information out of the ring structure is a complicated task, though, requiring careful numerical modeling. The planets’ mean motion resonances can create elaborate asymmetries in the ring structure, overlapping resonances can create regions interior to which grains can’t penetrate, and grain-grain collisions can have a dramatic effect on the shape of the structure. I have created a debris disk model that uses a “collisional grooming algorithm” to simultaneously treat resonant gravitational dynamics and grain-grain collisions, allowing us to model collisional disks (like that around Fomalhaut) self-consistently for the first time.
Preparing for Future Exo-Earth Imaging Missions
The inner few AU of our solar system is home to a diffuse cloud of dust, called zodiacal dust, which is released by colliding asteroids and outgassing comets. We’ve detected dust in the inner regions of other planetary systems, too. So future missions that aim to directly image Earth-like exoplanets will have to contend with the starlight reflected by these dusty exozodiacal clouds.
Exozodiacal dust has been identified as the largest source of uncertainty for future exo-Earth imaging missions. Not only can the diffuse haze of dust make it difficult to find exoplanets, but those exoplanets may in fact create clumpy structures within the dust cloud that makes finding the planet like looking for a needle in a haystack.
I am investigating the degree to which exozodiacal dust may be a problem for future direct imaging efforts. I model how planets interact with clouds of dust and synthesize images of structured exozodiacal clouds. I have developed a hybrid symplectic integrator for our models and implemented it on the Discover cluster at NASA Goddard Space Flight Center. Below are a few examples of the structures that planets can create in exozodiacal dust clouds.
Exozodi Simulation Catalog
Check out my catalog of exozodiacal ring structures. You can see how the geometry of resonant rings depend on planet mass, planet semi-major axis, and dust grain size. The models simulate collisionless debris disks of a single grain size around a Sun-like star. The dust gravitationally interacts with a single planet on a circular orbit to produce the asymmetric circumstellar rings shown in the catalog. For more information, see this paper.