My objective in science is to improve our ability to identify, track, and characterize the small bodies that surround us in the solar system—in essence, the what, where, and why of our planetary neighborhood. I'd like to understand the history they record and their behavior in various space environments to inform humanity's future interactions with them.
Every few days, coronagraphs like the LASCO instruments aboard the SOHO spacecraft capture the demise of yet another comet wandering too closely to the Sun. Despite outnumbering all other known comets combined, their brief apparitions and sky placement by the Sun hinders detailed studies of their properties and origins. I'm interested in new strategies to identify these comets and probe their physical and dynamical characteristics.
1I/ʻOumuamua, discovered in October 2017, is the first extrasolar small body identified in the solar system, and will likely not be the last. I participated in early observations of 1I (Ye+ 2017; arXiv:1711.02320) and placed bounds on the traceability of such objects (Zhang 2018; arXiv:1712.08059).
Near-Earth asteroids routinely impact Earth, or threaten to do so. Most are harmlessly small, and destroyed in Earth's atmosphere, but larger objects occasionally threaten human interests. Planetary defense covers strategies to mitigate these hazards. As an undergraduate at UCSB, I worked on one approach that considers laser ablation by phased laser arrays to deflect threatening asteroids (Zhang+ 2016; arXiv:1601.03690) and comets (Zhang+ 2019; arXiv:1904.12850).
Most periodic comets likely originated far beyond Neptune in the Kuiper belt or related structures like the scattered disk. Comet-sized (~1 km diameter) objects, however, are too faint to directly observe so far away with modern telescopes, obfuscating the origin story. We instead probe these "proto-comets" by monitoring for stars that briefly blink out from objects crossing in front of them ("occultations").
Several occultation surveys have already been conducted with varying levels of success. I work on the CHIMERA project at Caltech, an ongoing occultation survey performed with the Hale Telescope at Palomar Observatory. This survey will be by far the most sensitive to date in the sub-kilometer diameter range.
A small fraction of low mass stars and brown dwarfs are bright radio emitters, for reasons that are not entirely clear. Observational evidence points to gyrosynchrotron radiation and electron cyclotron maser instability (ECMI)—mechanisms perhaps best known for creating Jupiter's radio activity—as the source of the emission. In a first-year graduate research project at Caltech, I used very-long-baseline interferometry (VLBI) to probe the emission from a pair of such stars at very high spatial resolution. Results are slated to be announced mid-2019.