Astrobiology & The Search for Life
Searching for evidence of life on other planets will require powerful observatories, advanced instrumentation, creative observing strategies, and state-of-the-art statistical methods. Our group contributes to the demographic and methodological foundations on which biosignature searches will rest.
We work on four interconnected fronts. The first is quantifying η⊕ and its uncertainties so that mission yield estimates rest on defensible inputs (Hsu et al. 2020; He et al. 2026; Fernandes et al. 2025; Bryson et al. 2021). The second is probabilistic yield analyses and design trades for exoplanet surveys and future characterization missions such as the Habitable Worlds Observatory (Stark et al. 2024), including how astrophysical uncertainties translate into the science margin needed to robustly deliver 25 or more exoEarth candidates. The third is identifying the best nearby targets for direct-imaging follow-up of habitable-zone planets discovered via radial velocity — for example, GJ 251 c, a candidate habitable-zone super-Earth around a nearby M dwarf. The fourth is developing methods to characterize the surfaces and climates of potentially Earth-like planets through photometric variability, exploiting the time-resolved reflected light that future direct imaging missions will collect to map surface inhomogeneities, constrain cloud cover, and probe atmospheric conditions.
Key Projects
Frequency of Earth-like Planets (η⊕)
Quantifying η⊕, the occurrence rate of Earth-analogs in the habitable zones of Sun-like stars, and characterizing the uncertainties that limit it. Reliable estimates are a prerequisite for defensible mission yield calculations. Our work includes Bayesian analyses of Kepler data (Hsu et al. 2020), population-synthesis constraints from SysSim (He et al. 2026), and a review of why published estimates disagree and what observations are needed to converge (Fernandes et al. 2025).
Exoplanet Survey Design & Mission Yield
Probabilistic yield analyses and design trades for exoplanet surveys and future characterization missions such as the Habitable Worlds Observatory (HWO). We model how astrophysical uncertainties in stellar properties, planet occurrence, and zodiacal dust translate into the science margin for a mission that aim to characterize 25 or more exoEarth candidates. This work informs observatory design choices and helps quantify the risk of falling short of science requirements.
Photometric Characterization of Earth-like Planets
Developing methods to characterize the surfaces and climates of potentially Earth-like planets through photometric variability. Future direct imaging missions will collect time-resolved reflected light from exoplanets. We develop the statistical tools needed to extract surface inhomogeneities, constrain cloud cover fractions, and probe atmospheric conditions from these sparse, noisy light curves.
Selected Publications
- Discovery of a Nearby Habitable Zone Super-Earth Candidate Amenable to Direct Imaging
Beard, Corey et al. (2025), AJ, 170, 279. abstract doi - Are We There Yet? Challenges in Quantifying the Frequency of Earth Analogs in the Habitable Zone
Fernandes, Rachel B. et al. (2025), PASP, 137, 121001. abstract doi - Paths to robust exoplanet science yield margin for the Habitable Worlds Observatory
Stark, Christopher C. et al. (2024), Journal of Astronomical Telescopes, Instruments, and Systems, 10, 034006. abstract doi - The Occurrence of Rocky Habitable-zone Planets around Solar-like Stars from Kepler Data
Bryson, Steve et al. (2021), AJ, 161, 36. abstract doi - Extreme Precision Radial Velocity Working Group Final Report
Crass, Jonathan et al. (2021), arXiv e-prints, arXiv:2107.14291. abstract doi - Occurrence rates of planets orbiting M Stars: applying ABC to Kepler DR25, Gaia DR2, and 2MASS data
Hsu, Danley C., Ford, Eric B., Terrien, Ryan (2020), MNRAS, 498, 2249-2262. abstract doi - TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm Super-Neptune Orbiting an M-dwarf Host
Kanodia, Shubham et al. (2020), ApJ, 899, 29. abstract doi - A Sub-Neptune-sized Planet Transiting the M2.5 Dwarf G 9-40: Validation with the Habitable-zone Planet Finder
Stefansson, Gudmundur et al. (2020), AJ, 159, 100. abstract doi - A Mini-Neptune and a Radius Valley Planet Orbiting the Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the Habitable-zone Planet Finder
{Stef\'ansson}, Gu\dhmundur et al. (2020), AJ, 160, 259. abstract doi - Occurrence Rates of Planets Orbiting FGK Stars: Combining Kepler DR25, Gaia DR2, and Bayesian Inference
Hsu, Danley C. et al. (2019), AJ, 158, 109. abstract doi - The Next Steps for Understanding Habitability of Exoplanet Waterworlds
Kite, Edwin S., Ford, Eric B. (2019), 130-082. abstract - Exoplanet Diversity in the Era of Space-based Direct Imaging Missions
Kopparapu, Ravi Kumar et al. (2019), \baas, 51, 12. abstract doi - Habitability of Exoplanet Waterworlds
Kite, Edwin S., Ford, Eric B. (2018), ApJ, 864, 75. abstract doi - Kepler-1647b: The Largest and Longest-period Kepler Transiting Circumbinary Planet
Kostov, Veselin B. et al. (2016), ApJ, 827, 86. abstract doi - The Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures
Wright, Jason T. et al. (2016), ApJ, 816, 17. abstract doi - An Earth-Sized Planet in the Habitable Zone of a Cool Star
Quintana, Elisa V. et al. (2014), Science, 344, 277-280. abstract doi - Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone
Borucki, William J. et al. (2013), Science, 340, 587-590. abstract doi - Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star
Borucki, William J. et al. (2012), ApJ, 745, 120. abstract doi - Characteristics of Kepler Planetary Candidates Based on the First Data Set
Borucki, William J. et al. (2011), ApJ, 728, 117. abstract doi - Kepler Planet-Detection Mission: Introduction and First Results
Borucki, William J. et al. (2010), Science, 327, 977. abstract doi - From Discovery to Understanding: Principles for Maximizing Scientific Return on Exoplanet Research
Ford, Eric B. et al. (2009), 2010, 80. abstract - Identifying the Rotation Rate and the Presence of Dynamic Weather on Extrasolar Earth-like Planets from Photometric Observations
{Pall\'e}, E. et al. (2008), ApJ, 676, 1319-1329. abstract doi - Role of Dynamical Research in the Detection and Characterization of Exoplanets
Ford, Eric B. et al. (2007), arXiv e-prints, arXiv:0705.2781. abstract doi - The 4-m space telescope for investigating extrasolar Earth-like planets in starlight: TPF is HST2
Brown, Robert A. et al. (2003), 4854, 95-107. abstract doi - Early-Type Stars: Most Favorable Targets for Astrometrically Detectable Planets in the Habitable Zone
Gould, Andrew, Ford, Eric B., Fischer, Debra A. (2003), ApJL, 591, L155-L158. abstract doi