Drawing of a comet

Image: Drawing of a generic comet, showing its dust tail (white), ion tail (blue), and gas coma (green)

My research interests include near-Earth objects, sungrazing comets, and other small bodies in the solar system and beyond. I would like to understand the role of these objects in planetary systems and how they behave in various astrophysical environments. Such understanding is a key to successfully interacting with these interplanetary neighbors, necessary to ensure our future livelihood on Earth and beyond. Comets in particular are also fun to observe in the sky as they change from night to night, often unpredictably.

I've also been known to make digital drawings of objects or phenomena related to my research, such as the ones on this page. You may have also encountered them on talks or posters I've present at conferences. I find that these provide me, and hopefully my audience, a reminder that what I'm studying is very real and physical below all the math and abstraction I've buried it under.

I've been involved with research in various aspects of planetary astrophysics with several different groups. Some of this work has been featured in various media outlets. A few of these projects are discussed below.

Sungrazing Comets

Jul–Aug 2016; Jun–Aug 2017: Sungrazer Project; PI: Karl Battams

Near-Sun comets approach to within a few solar radii of the Sun where they sometimes become visible to imagers aboard the SOHO and STEREO spacecraft. Some of these comets are short-period objects. Some might not be comets at all and may actually be asteroids exhibiting comet-like features while vaporizing under the intense heat. Others comprise groups that are the products of cascading fragmentation of ancient progenitor comets. I analyzed the morphology of many of these comets in LASCO C2 images through a PSF analysis of its field of view.

Planetary Defense by Directed Energy

Jul 2014–Jun 2017: UCSB Deepspace; PI: Philip Lubin

Comet deflection by laser heating

Threatening near-Earth asteroids and comets may be deflected through laser heating. A laser beam directed onto the surface of a threatening asteroid or comet begins to vaporize it, producing a plume of ejecta. The plume exerts thrust on the target which slowly shifts its orbit to avert an impact.

I developed orbital simulations to quantify the deflection under various laser configurations and impact scenarios. Some of the earlier results, focusing primarily on asteroids, are discussed in Zhang et al. (2016).

More recent work focuses on the problem of comet deflection. Due to their often highly inclined and eccentric orbits, comets pose an often insurmountable challenge for any approach that requires intercepting the comet by spacecraft. However, directed energy may be used to deflect comets remotely with a laser in Earth orbit or even on the ground (with adequate adaptive optics technology). Comet deflection force is modeled in a similar fashion to the natural nongravitational forces experienced from solar heating. Results on these simulations are currently pending peer-review.