I maintain a library of my publications on the SAO/NASA Astrophysics Data System (ADS) here. My ORCiD, which can be used to track my publications, is 0000-0001-6396-8439. My CV can be found on my academic webpage, here.


My research interests concern the origin and formation of exoplanets and sub-stellar objects. The big questions that drive my research are “how do planetary systems form generally,” “how can we distinguish between planets and other substellar objects, such as Brown Dwarfs,” and “how unique is our solar system in the context of star and planet formation?” I use big telescopes, special optics, and computer algorithms to study the orbits, growth, and composition of planets and sub-stellar objects. Currently, I am using direct imaging, radial velocities, and optical interferometry to work towards answering my driving questions. I love observational astronomy and telescope operations.

During my thesis research at JHU, I am primarily using the coronagraphic NIRCam and MIRI instruments on JWST, and the VLTI/GRAVITY instrument from the ground.

Direct Imaging in space with JWST

The James Webb Space Telescope (JWST) is a 6.5m observatory that views the universe in infrared wavelengths of light. The infrared is particularly difficult to observe from the ground, because the water and carbon-dioxide in the Earth’s atmosphere absorbs and re-emits a lot of infrared radiation, scrambling our view of the infrared universe. Most planets emit their light in infrared wavelengths, so you could imagine that having a telescope without the atmosphere in the way is great news for studying other planets.

JWST has a handful of coronagraphic instruments, which can be used to block the light from bright stars, in order to reveal the faint planets that orbit them. I work with the JWST Telescope Scientist Team, guided by my thesis advisor Laurent Pueyo, to recover the light from planets in our images, and learn more about the atmospheres of these strange worlds.

I participated in the JWST Early Release Science program for direct imaging, and am working on forthcoming observations from our TST Guaranteed Time Observations. I am the Co-PI of two JWST cycle 2 programs to directly image two fascinating planets: one young, and one old. Stay on the lookout for more exciting news from my JWST work.

Interferometric observations of exoplanets & sub-stellar objects with the ExoGRAVITY collaboration

The European Southern Observatory’s Very Large Telescope Interferometer (VLTI) hosts the GRAVITY instrument, built for “precision narrow-angle astrometry and interferometric imaging.” That means it combines the light measured from four of the largest telescopes in the world into one observatory that is able to measure the positions of bodies in space with unprecedented precision. I work with the ExoGRAVITY collaboration to measure the motion and color of exoplanets and sub-stellar companions with this instrument.

Specifically, I’m currently training to improve the data reduction of our collaboration’s results, guided by my thesis advisor Laurent Pueyo and the ExoGRAVITY collaboration’s leaders. In addition to this broader goal of improving data reduction, I’m building upon my science analysis skills by formulating goals for further analysis of collaboration data. I’m working on orbital analysis (similar to my undergraduate work on HD 142527 B, but at much higher precision) using the orbitize! tool, and modeling the observed spectral signatures of our targets with different atmospheric model codes. I’m guided in this work by my advisor David Sing, and by collaboration members. I’m in the process of writing a handful of 1st author papers that incorporate GRAVITY observations of planets and sub-stellar objects, like AF Leporis b, and helping to formulate observing time proposals with the collaboration. I’ve been awarded over 24 hours of VLTI time as a PI, equivalent to more than 4 days of 8m telescope time.

GRAVITY’s precision is nearly 200x better than single-telescope observations, as demonstrated by this figure from GRAVITY Collaboration et al. (2019, A&A 623, L11). The motion of the exoplanet HR 8799 e is fit by yellow orbital trajectories, while grey crosses represent single-telescope observations of the planet. The black cross represents the first GRAVITY observation of the target, at nearly 200x the precision.

My first paper using VLTI/GRAVITY observations of the brown dwarf HD 72946 B is available on arXiv, and was published in the Astrophysical Journal. I was second author on a paper about VLTI/GRAVITY observations of the gas giant planet HIP 65426 b, which was published in the Astronomical Journal. My third first author paper, detailing VLTI/GRAVITY observations of the young brown dwarf HD 136164 Ab (also known as HIP 75056 Ab) is accepted to the Astronomical Journal and will appear in December 2023 / January 2024.

GRAVITY can measure the spectrum of a planet or brown dwarf, by breaking up the light into its component wavelengths (or colors). Different molecules (even different kinds of clouds) in a planet’s atmosphere shape the spectrum, and we can compare our observations to models of what the planet’s atmosphere might be made out of. This figure (from Balmer et al. 2023, ApJ, in press) compares atmospheric models with different kinds of clouds to our spectral observations of the brown dwarf HD 72946 B.
A figure from an upcoming paper, showing VLTI/GRAVITY observations of a brown dwarf orbiting a star. GRAVITY allows us to measure the eccentricity (how circular an ellipse is) of the orbits of these objects, which can tell us how they formed.

I’ve presented some of my work with GRAVITY and the VLTI at the In the Spirit of Lyot ’22 and Coolstars 21 conferences, among other venues. For more on this work, check out my poster and talk slides.

Undergraduate Research

Most of my work during my undergraduate studies involved direct imaging, simulations of direct imaging, and the aggregation of direct imaging results. There’s a visceral satisfaction in taking a picture of something hundreds of light years away (especially if that something is a planet) and using that picture to understand something deeper about the physics of the universe.

A detailed analysis of direct images of the proto-star HD142527B

Star and planet formation are linked! For about two years I’ve studied the distant star system HD 142527, in particular I’ve tried to understand the orbit of the binary stars within this system and the rate of growth of the smaller star, HD 142527 B. This small star is embedded in a disk of gas and dust that surrounds a larger star (HD 142527 A), and by studying how the smaller star moves through this disk, we can better understand and model how stars and planets interact with protoplanetary disks. This research is important because we believe small rocky planets like Earth form from these protoplanetary disks. In binary systems like HD 142527 (or, like the fictional Tatooine from Star Wars, or the Klendathu System from Starship Troopers) the orbit of the two stars around each other could affect how rocky planets eventually form.

Figure 5 from my paper “Improved Orbital Constraints and Hα Photometric Monitoring of the Directly Imaged Protoplanet Analog HD 142527 B”

This work has been accepted for publication in the Astronomical Journal, and is available to read for free on arXiv here. I wrote an in-depth blog post on it here and a thread on twitter here. I’ve presented this research at the Coolstars 21 meeting in Summer 2022, the STScI 2021 Spring Seminar (poster below) and at the 237th Meeting of the AAS (interactive poster linked here).

In order to image the fainter companion star HD 142527 B, I remove the bright starlight from HD 142527 A from my images in a process referred to as “Point Source Function (PSF) subtraction” or “starlight subtraction.” I use a specific kind of starlight subtraction known as Angular Differential Imaging (ADI), leveraging the rotational diversity of a time series of observations, and two channel Simultaneous-Spectral Differential Imaging (S-SDI), leveraging the excess luminosity exhibited by objects undergoing accretion to remove starlight and disk structure from my images. I do this with the python implementation of the fancy sounding Karhunen-Loeve Image Processing (pyKLIP) algorithm. I essentially use the astronomy equivalent of facial recognition software to create a model of the light from HD 142527 A, which I subtract from images containing both A and B, in order to reveal B. I did this work under the tutelage of Dr. Kate Follette, who is the PI of the Giant Accreting Protoplanet Survey (GAPlanetS), a survey which uses the same techniques to search for baby planets!

Q: “What is your website logo?”

A: An artifact of KLIP starlight subtraction process is “self-subtraction” which occurs because the modeled PSF is constructed from a finite series of images (good explanation here). So when you reveal a planet using KLIP or a similar algorithm, the signal of the planet is this emblematic little butterfly thing, with the planet light surrounded by two self-subtraction lobes. My website logo in particular is one of the results of my undergraduate thesis research.

Simulating Exozodi Yield

During the summer of 2020 (amid other things) I worked remotely with Dmitry Savranski in the Space Imaging and Optical Systems Lab (SIOS Lab) at Cornell University. I used EXOSIMS, a direct imaging simulation suite developed by SIOS lab, to predict the yield of the miniaturized Distributed Occulting Telescope (mDOT), a novel cubesat proposed by some very smart people at Stanford University which will demonstrate the effectiveness of an occulting star shade in negating starlight to observe exoplanets and circumstellar dust. You can view slides from a presentation I gave on this research here.

Transition Disk Database

The Transition Disk Database (TDD) is an aggregation of transition disk morphology and properties. I presented the results of this literature review at the 235th meeting of the American Astronomical Society (see my “betterposter” design here). The project has evolved dramatically since I pursued other research, and you can follow the results at http://follettelab.com/

This is a picture of me presenting my poster on the TDD at the 235th meeting of the AAS in Honolulu, HI.

Very Low Mass Variability

I observed very low mass (VLM) stars using the Half-Degree-Imager on the WIYN 0.9m telescope atop Kitt Peak National Observatory on the Tohono O’odham Nation. I presented some of this research with my collaborator Lena Treiber to the Five College Astronomy Department (who paid for my trip to KPNO). You can see our poster and some very beautiful images of the Taurus star forming cloud below. I kept an online journal during the spring semester, which you can read here.

Teachers Assistant work and Star Clusters

I worked as a TA for many of the astronomy course offerings at Amherst College (ASTR 112: Alien Worlds, ASTR 337: Observational Techniques I, and ASTR 341: Obs. Tech. II). I set up and operated the 11in Cassegrain telescopes atop the New Science Center’s observatory, working under one of the coolest people I know, Sarah Betti. We’ve gotten some pretty good data, given local weather conditions and elevation, which I’ve used to fit isochrones to open clusters.