Research

My research interest are varied, but most of my work centers on Saturn's rings. My thesis studied the way that ring edges spread in time when there is no moon to contain them. Earlier work had generally assumed fluid-like characteristics to the edges and treated the spreading that way. However, the scale over which spreading occurs, although signficantly larger than a ring particles, is not significantly larger than the wake-like aggregates that form in self-gravitiating rings. (The aggregates are temporary and form more strongly the farther away from the planet — and the planet's tidal forces — you look.) To reduce the reliance on such assumptions, I used my own N-body code to simulate the ring edges. It was quite a challenge, algoritmically, but also fun (most days). The results were intriguing (the rings don't quite spread like fluids) and there's still a lot to do in that area. Someday, hopefully soon...

More recently, I did a post-doc on the Cassini mission at CICLOPS with Carolyn Porco. My work there was in a related vein, but I built up a lot of new skills. My main work was to study the photometry of Saturn's rings using a ray-tracing code to conver N-body models into simulated brightnesses at various geometries. Although we've never resolved a ring particle in an image and we've seen only unusually large wake-like clumps, the photometry of the rings tells us quite a bit out the particles and clumps, inferentially. I'm still working on this, although at a lower pace, what with my teaching schedule.

I've also been interested in topics related to moon capture and moon loss during planet migration. It seems (from our studies) that the migration process had have significant effects on the moons' orbits, pumping up eccentricity and inclination and eventually causing them to become unbound from the planet. The most intriguing thing we found in this area was that the retrograde moons are more stable than the prograde moons; this wasn't entirely unexpected, based on other work regarding orbits, but it does suggest that the "hot Jupiters" may have more retrograde moons than unmigrated planets.

Additionally, when I first arrived at CICLOPS, before I had really taken on any research there, I started playing around with the problem of inferring moon-masses from their effects on nearby rings. Earlier work had used some analytic approximations to solve this, but it seemed worthwhile to check those assumptions with numerical techniques. The results showed that the analytic method worked well for the moon Pan, but as the moons (and the gaps they create) get smaller, the formula starts to over-estimate their masses. Also, as a bonus, in doing this research, we realized that in small gaps, the moons' eccentricities and inclinations can create time-variable waves on the gap-edges. Thus, single snapshots of the edges are not reliable indicators as to the masses of the moons. We also realized that Daphnis' inclined orbit is likely to create vertical waves at the Keeler gap's edge. This was confirmed during Cassini's equinox missions with stunning photos of the shadows of those vertical features.

Lately, I've been working with students on subjects like vertical structure in Saturn's rings and the vality of certain widely-used approximations in ring simulations. Working with students has been fun and rewarding; each of them has brought a different skill to our work and taught me some new tricks. My only regret is that they eventually move on...

If you're bored on want to see what I was like as an undergrad, there's also my Comps project on planet formation. I'm a little embarrassed by it now, but I'm also still proud of how much I taught myself about a new subject.

Also, once upon a time I worked in planetary magnetospheres. It was my first two years of grad school with the wonderful Nick Schneider and it was exciting, but it turned out that I was better-suited to dynamical astronomy. Still, I've still feel a little kinship to the magnetosphere people.

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