Sagan Postdoctoral Fellowship Recipients

2015 Postdoctoral Fellows

for additional information on each Fellow's project, please click on the project title

JPL press release announcing the 2015 Carl Sagan Fellows

more information on the Sagan Fellowship program

Courtney Dressing
California Institute of Technology

Characterizing Small Planets Orbiting Small Stars

I grew up in Alexandria, VA and received a bachelor's degree in astrophysical sciences from Princeton University in 2010. I will receive a Ph.D. in Astronomy and Astrophysics from Harvard University in May 2015. I am currently 27 years old.

I've been interested in astronomy and space exploration since elementary school and I spent many childhood evenings stargazing. My family was very supportive of my early interest in space and agreed to an impressive number of outings to the National Air and Space Museum. The more I learned about space, the more curious I became about whether there was life elsewhere in our Solar System and whether any other stars harbored habitable planets.

As a Sagan Fellow, I will investigate the properties of planets orbiting small stars known as red dwarfs. Red dwarfs are significantly cooler than the Sun, so the "habitable zone" within which planets could have liquid water on their surfaces is located much closer to the star. Due to the small sizes and close-in habitable zones of red dwarfs, it is much easier to detect a potentially habitable planet orbiting a red dwarf than a Sun-like star. I will conduct follow-up observations of small K2 planet candidates orbiting red dwarfs in order to determine which planet candidates are likely planets and which are false positives. I will then constrain the radii and temperatures of K2 red dwarfs using near-infrared spectra and measure the masses of a subset of small planets by obtaining highly precise radial velocities. Finally, I will investigate how the properties and occurrence of planets orbiting low-mass stars depends on stellar mass and metallicity.

Daniel Foreman-Mackey
University of Washington

Flexible and Robust Inference of the Exoplanet Population

I grew up in Ontario, Canada and received a Master's degree from Queen's University in Kingston, Ontario. I then moved to New York University where I expect to receive my PhD from the Physics department in Spring 2015. My doctoral research was focused on the application of probabilistic modeling to interesting datasets and questions in astronomy. Recently, I've been studying the existing Kepler dataset at all levels: planet discovery, characterization, and population inference.

I was originally drawn to astronomy by the exciting open questions and the wealth of publicly available datasets. The field of exoplanets, especially at the intersection between observation and theory, is an ideal place to apply novel data analysis techniques with the possibility of exciting scientific discovery.

As a Sagan Fellow, I plan to develop rigorous probabilistic methods and open source tools for studying the population of exoplanets based on the available array of heterogeneous datasets. In particular, I will focus on the physically and dynamically interesting questions of very long period planets and the multiplicity-mutual inclination distribution of planetary systems. The tools I develop will be useful for existing datasets and the forthcoming onslaught of data from surveys like K2 and TESS.

Jonathan Gagne
Carnegie Institute for Science

Locating the Young, Isolated Planetary-Mass Objects in the Solar Neighborhood

I grew up in a small town north of Montreal and moved there to study Physics. I became interested in my current research area while I was an undergrad at Université de Montréal and had the chance to complete a summer internship related to the direct imaging of exoplanets and brown dwarf surveys under the direction of René Doyon. My PhD project, which consisted in the search for isolated brown dwarfs in young moving groups under the direction of David lafreniére and René Doyon, represented a great marriage of these two topics. I am now 27 years old and submitting my PhD thesis in April 2015. I will then bring my project to the next level during my Sagan Fellowship at Carnegie Institute for Science, by identifying young brown dwarfs with only a few times the mass of Jupiter and exploring the connection between their atmospheres and those of giant exoplanets.

I will extend the successful survey that I led during my PhD thesis to locate the elusive coldest, isolated planetary-mass members of young moving groups. I will use the suite of high-end instruments at the Las Campanas observatory to characterize these discoveries with a parallax program, optical and near-infrared low- and mid-resolution spectroscopy and high-precision photometric measurements. This research will allow to explore the connection between the atmospheres of brown dwarfs and those of giant exoplanets, and will put strong constraints on the initial mass function down to a few times the mass of Jupiter, hence testing the recent prediction that the spatial density of isolated jupiter-mass objects is twice as large as that of stars.

Paul Robertson
Pennsylvania State University

Spotting Blue Planets Around Spotted Red Stars:
Removing Stellar Activity from Radial Velocities of M Dwarf Stars

I grew up in western North Carolina, and received my bachelor's degree from the University of North Carolina in 2008. In 2013, I received my PhD from the University of Texas at Austin. I am a postdoctoral fellow at Penn State University's Center for Exoplanets and Habitable Worlds, where I am currently helping to build the Habitable Zone Planet Finder (HPF) spectrograph.

As a young child, I watched a documentary on the Voyager mission, and was enchanted by the images of our Solar Systems outer planets. When astronomers discovered the first extrasolar planets a few years later, I decided I had to be part of the search for new worlds.

As a PhD student at Texas, I realized that the planets I am most eager to find - small planets in the habitable zones of nearby M stars - will be hidden by noise from their parent stars. My project aims to improve our understanding of stellar noise in exoplanet searches, and improve methods to correct it. This work will be crucial for the success of the HPF survey of planets around M stars in the solar neighborhood.

Tyler Robinson
University of California, Santa Cruz

Bridging the Theory Gap: Developing a Novel Cloud Model for Exoplanets

I was born in Cincinnati, Ohio, and grew up north of Phoenix, Arizona. I studied physics and mathematics at the University of Arizona, graduating in 2006. Following that, I moved to Seattle for my graduate work in astronomy and astrobiology at the University of Washington, where I received my Ph.D. in 2012. I then completed a two-year appointment as a NASA Postdoctoral Program Fellow at NASA Ames research center. I am 30 years old.

I can distinctly remember the first time I experienced a sense of awe for the cosmos: it was while viewing the comet Hale Bopp from the rim of the Grand Canyon when I was 13 years old. I developed a love of mathematics in high school, and combined my passions for math and astronomy as an undergraduate. While a Ph.D. student in the University of Washington Astrobiology Program, I was able to explore astrophysical and planetary science questions with an eye towards, one day, detecting and characterizing a Pale Blue Dot around a distant star.

As a Sagan Postdoctoral Fellow, I will study cloud processes in planetary atmospheres. Clouds sculpt the spectra of almost all planets, and confound observational studies of many exoplanets. To inform the interpretation of existing and future exoplanet observations, I aim to develop accurate and efficient tools for simulating and understanding cloud formation and dynamics in exoplanet atmospheres.

Leslie Rogers
University of California, Berkeley

Searching for Water in Distant Worlds

I grew up in Yarmouth, Nova Scotia, on the east coast of Canada. I pursued undergraduate studies in honors physics-mathematics at the University of Ottawa, and then earned a PhD in physics from MIT in 2012. After defending my thesis, I moved to Caltech as a Hubble Postdoctoral Fellow.

Two memories stand out in my mind as having sparked my interest in astronomy and planetary science at a young age: watching the Perseid meteor shower with my dad from our back deck (there's not much light pollution in Yarmouth), and repeatedly borrowing Isaac Asimov's New Library of the Universe series from the library to pore over the stunning photos of the Solar System giant planets returned by Voyager. I am very grateful to now have the chance to explore the diversity of planets as my profession!

In my research, I study the interior structure, formation, and evolution of exoplanets that are Neptune-size and smaller. It is a matter of ongoing debate whether the abundance of Neptune-size planets discovered by Kepler formed in situ at orbital separations (inside 0.4AU) near where they are currently observed or instead formed beyond the snow line (where water condenses to ice in the protoplanetary disk) before later migrating inward toward the star. As a Sagan Fellow, I will pursue three novel complementary approaches to constrain the bulk water content of distant exoplanets, a powerful tracer of the planets' formation locations. Advancing models of planet interior structure, planet evolution, and population statistics, I will lay the theoretical foundation to extract constraints on planet bulk compositions and formation pathways from atmospheric transmission spectra, exoplanet radio aurora emissions, and the accumulating statistical ensemble of planet mass-radius measurements.