Research Interests

Time Domain Science

I use time-series data from space to learn things about stars, planets and galaxies. I focusing on the discovery and characterization of exoplanet but have also studied stellar oscillations, and galactic transients.

Statistical Methods

I enjoy applying novel statistical techniques to data-based problems in astrophysics. Mostly this involves using tools like Gaussian Processes and Markov Chain Monte Carlo.

Planet Formation

I use N-body simulations to model the formation and evolution of rocky planets, measure impact rates, and track water delivery. Our Solar System formed one temperate planet that has long-lived oceans. Why did this happen, and are we an anomaly?

Stellar Activity

I lead a large multiwavelength project to measure the rate and energies of stellar flares with data spanning radio to X-ray. The goal is to determine whether planets around cool stars are good places to search for life

About Me

I have worked NASA flight projects since 2011, including pre- and post-launch operations. I am Director of the TESS Science Support Center, and TESS Associate Project Scientist. While based at NASA's Goddard Space Flight Center, I work for the University of Maryland, Baltimore County.

My primary scientific interests lie in the analysis of data from space and ground-based telescopes to infer properties of exoplanets and their host stars. This has led to a number of major discoveries including the detection of the smallest known planet, the detection of the first super-Earth-sized planet orbiting in the habitable zone of a Sun-like star, and the detection of the first Earth-sized planet in the habitable zone of another star.

I grew up in the city of Sheffield in Northern England, UK. My undergraduate studies were performed at the University of Leeds, UK where I obtained a Bachelors degree in Physics with Astrophysics in 2006. My Masters thesis work was performed at the Jodrell Bank Observatory, part of the University of Manchester. I obtained a Master of Science degree in 2007 for work to understand Galactic dust emission. I then moved to Northern Ireland for my doctoral studies where I worked at the Armagh Observatory. I was co-supervised, and was awarded my Ph.D. by, University College London in 2011. I worked on understanding the population of ultra-compact white dwarf binaries.

After my postgraduate studies, I was appointed to the Kepler Guest Observer Office at NASA Ames Research Center, California as a research scientist.

In 2014 I was promoted to Director of the Kepler/K2 Guest Observer Office. I led a team responsible for developing proposal calls, organizing proposal reviews, providing critical support to the scientific community and developing software to enhance output from Kepler and K2. I was part of the small team that pioneered the K2 mission, utilizing the Kepler spacecraft after the loss of fine pointing control. I served on the science and mission leadership teams for K2.

In 2017 I moved to NASA's Goddard Space Flight Center in Greenbelt, Maryland to work on the TESS mission. I initially, served as Deputy Director and then Director of the TESS Guest Investigator Program, and as Associate Project Scientist. I am a member of the Exoplanet Exploration Program Executive Committee.


I've published over 110 refereed papers, on all manner of topics in astrophysics ranging from planets in our solar system to distant supernovae. Below are a list of papers that I've been a part and am especially proud of, or I think are particularly interesting for one reason or another.

The L 98-59 System: Three Transiting, Terrestrial-Sized Planets Orbiting a Nearby M-dwarf

We reported the discovery of three terrestrial-sized planets transiting L 98-59, a bright M dwarf at a distance of 10.6 pc. The planets radii range from 0.7 REarth to 1.3 REarth. The planets are prime targets for future transit spectroscopy with the James Webb Space Telescope. (Kostov, Schlieder, Barclay et al. 2019, AJ)

A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)

In this paper wemade estimated of how many exoplanets the TESS mission would detect, the physical properties of the detected planets, and the properties of the stars that those planets orbit. The hope was that it would be useful for people planning future observations. The simulation data are available from Figshare. These simulations seems to have done a pretty good job at predicting the real distribution of TESS planets. (Barclay, Quintana and Pepper, 2018, ApJS)

The Demographics of Rocky Free-floating Planets and their Detectability by WFIRST

I wanted to make a prediction about what WFIRST will find. During tplanet formation, material in the disk either remains bound to the star as part of either a planet, a smaller celestial body, or makes up part of the the interplanetary medium; falls into the star; or is ejected from the system. We used dynamical models to probe the abundance and properties of ejected material during late-stage planet formation and estimate their contribution to the free-floating planet population. We predicted that the space-borne microlensing search for free-floating planets from the WFIRST will discover up to many Mars-mass planets, but few free-floating Earths. (Barclay, Quintana, Raymond and Penny, 2017, ApJ)

An Ancient Extrasolar System with Five Sub-Earth-size Planets

This is definitely my favorite planetary system. We reported the discovery of five transiting planets with sizes between those of Mercury. The host star, Kepler-444 is the densest star with detected solar-like oscillations. We used asteroseismology to directly measure a precise age of 11.2 Gyr for the host star, indicating that Kepler-444 formed when the universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the universe's 13.8 billion year history, leaving open the possibility for the existence of ancient life in the Galaxy. (Campante, Barclay, Swift et al., 2015, ApJ)

The Five Planets in the Kepler-296 Binary System All Orbit the Primary: A Statistical and Analytical Analysis

In this paper we used a neat statistical technique determine the host star for five planets. Kepler-296 is a binary star system with two close M-dwarf components and five transiting planets. However, the planets could in principle orbit either star. Using importance sampling, we compared the model probabilities under the priors of the planets orbiting either the brighter or the fainter component of the binary. A model where the planets orbit the brighter component, Kepler-296A, is strongly preferred by the data. (Barclay, Quintana, Adams et al., 2015, ApJ)

Radial Velocity Observations and Light Curve Noise Modeling Confirm that Kepler-91b is a Giant Planet Orbiting a Giant Star

Kepler-91b is a rare example of a transiting hot Jupiter around a red giant star. However, the planetary nature of Kepler-91b, was called into question. The star exhibits temporally correlated noise due to stellar granulation which we modeled as a Gaussian Process simultaneously with transit, phase curve and radial velocity models. We hypothesized that it is this noise component that led previous studies to suspect Kepler-91b was a false positive. This is one of the first times that GPs were used to model stellar variability.(Barclay, Endl, Huber et al., 2015, ApJ)

An Earth-Sized Planet in the Habitable Zone of a Cool Star

This was the first Earth-sized planet in the habitable zone of another. We presented the detection of Kepler-186f, a 1.1 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized. The intensity and spectrum of the star’s radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form. (Quintana, Barclay, Raymond, et al., 2014, Science)

A sub-Mercury-sized exoplanet

Here we reported a planet significantly smaller than Mercury. This tiny planet is the innermost of three that orbit the Sun-like host star, which we designated Kepler-37. We used asteroseismology to determine the properties of the host star. Kepler-37b is still the smallest known planet. (Barclay, Rowe, Lissauer, et al., 2013, Nature)

Recent Publications

Contact Me

Reach out

If you're looking to get in touch with me, the best method is email. For most issues you're best contacting me on For NASA business (anything about the TESS GI Program, for example) please use my NASA address


Have an astronomy, data science, proposal preparation, anything else project that you'd like someone to consult on? Perhaps I can help. I have a registered sole proprietorship business in Maryland for consulting work. I've done previous work for a lovely company called Under Lucky Stars.