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Joshua Pepper

Joshua Pepper

Associate Professor

Lewis Lab 413

PhD in Astronomy, The Ohio State University

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Research Areas

Additional Interests

  • Exoplanets
  • Methods to characterize exoplanet signals in microlensing surveys
  • Discovery and behavior of pulsating stars
  • Identifying and measuring the properties of eclipsing binary stars
  • Detecting the eclipses of disks in binary star systems
  • The rotation of stars in open clusters
  • Astrobiology and the search for life

Research Statement

Joshua Pepper is an astrophysicist who specializes in the discovery and characterization of extrasolar planets - planets that orbit other stars.  He built and operated a pair of small robotic telescopes (called KELT) to detect transiting planets, discovering 26 extrasolar planets to date.  He has worked on a number of large sky surveys that observe stars and galaxies in both photometry and spectroscopy.  For many years he worked as part of the science team developing the Transiting Exoplanet Survey Satellite (TESS), a NASA space telescope dedicated to discovering small planets orbiting nearby stars all over the sky.  TESS launched in 2018 and is a cornerstone of the NASA search for new worlds.  


My astronomy career started as an undergraduate at the Department of Astrophysical Sciences at Princeton University.  For my junior-year projects, I worked with Professors Bohdan Paczynski and David Spergel, modeling the optical afterglows of Gamma-Ray Bursts.  For my senior thesis, I worked with Professor Michael Strauss to identify Active Galactic Nuclei in the commissioning data from the Sloan Digital Sky Survey.

After graduating, I spent a year working as a business consultant in Manhattan at the AnswerThink corporation.  I then moved to Columbus, Ohio, to start my PhD at the Department of Astronomy at the Ohio State University.  My research soon focused on methods for detecting transiting planets.  I worked with Professor Andy Gould to determine how to detect transiting planets around bright stars, and our analysis showed that an inexpensive telescope configuration operating an all-sky survey could optimally detect these objects. 

Deciding (naively) that it would be straightforward to design, build, and deploy a robotic telescope, use it to conduct a survey, and gather, reduce, and analyze the data for my PhD, I worked with Andy and Professors Darren Depoy and Rick Pogge to build the KELT telescope.  Somehow, we managed to do it, and I then worked with Rick as my advisor, along with Professors Scott Gaudi and Kris Stanek to analyze the data to find exoplanets.  We did not find any new planets immediately.  That was because we had vastly underestimated the required signal for transit detection, along with the huge numbers of false positives, the rarity of the hot Jupiter planets we were trying to find, and systematic noise in wide-field surveys.  We did, however, detect large numbers of variable stars.

From OSU, I moved to the Department of Physics and Astronomy at Vanderbilt University, where I became the VIDA postdoctoral fellow.  The VIDA program is the Vanderbilt Initiative in Data-intensive Astrophysics, run by Professor Keivan Stassun, which concentrates on astrophysical science that uses large data sets or amounts of computation.  At Vanderbilt, I built a twin of KELT, and deployed it to Sutherland, South Africa, where it became the KELT-South telescope, and the original telescope was renamed KELT-North.  By the end of my time at Vanderbilt, the KELT project began to bear fruit, with 4 planets discovered, more on the way, and an enormous amount of data that will be used for years to come.

In 2013, I became an assistant professor in the Physics Department at Lehigh University.  Based on that experience I wrote a guide to Navigating the Faculty Job Search that you can find on the AstroBetter blog and wiki. I have an appointment at Vanderbilt University as an adjoint professor, and I am the director of the KELT-South telescope and a leader of the KELT survey.  Although KELT is the primary focus of my work, I also work in a number of other areas that relate to exoplanets and time-domain astronomy. 

In 2018 I was tenured and promoted to associate professor at Lehigh.

Recent Publications

  • Pepper, J., Krupińska, O. D., Stassun, K. G., et al., 2019, “What Does a Successful Postdoctoral Fellowship Publication Record Look Like?”, Publications of the Astronomical Society of Pacific, 131, 4501
  • Grieves, N., Ge, J., Thomas, N., et al., 2018, “Chemo-kinematics of the Milky Way from the SDSS-III MARVELS survey”, Monthly Notices of the Royal Astronomical Society, 481, 3244
  • Huang, C. X., Burt, J., Vanderburg, A., et al., 2018, “TESS Discovery of a Transiting Super-Earth in the pi Mensae System”, The Astrophysical Journal Letters, 868, 39
  • Ziegler, C., Law, N. M., Baranec, C., et al., 2018, “Measuring the Recoverability of Close Binaries in Gaia DR2 with the Robo-AO Kepler Survey”, The Astronomical Journal, 156, 259
  • Barclay, T., Pepper, J., & Quintana, E. V. 2018, “A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)”, The Astrophysical Journal Supplement Series, 239, 2
  • Collins, K. A., Collins, K. I., Pepper, J., et al., 2018, “The KELT Follow-up Network and Transit False-positive Catalog: Pre-vetted False Positives for TESS”, The Astronomical Journal, 156, 234
  • Stassun, K. G., Oelkers, R. J., Pepper, J., et al., 2018, “The TESS Input Catalog and Candidate Target List”, The Astronomical Journal, 156, 102
  • Martioli, E., Colón, K. D., Angerhausen, D., et al., 2018, “A survey of eight hot Jupiters in secondary eclipse using WIRCam at CFHT”, Monthly Notices of the Royal Astronomical Society, 474, 4264
  • Johnson, M. C., Rodriguez, J. E., Zhou, G., et al., 2018, “KELT-21b: A Hot Jupiter Transiting The Rapidly-Rotating Metal-Poor Late-A Primary Of A Likely Hierarchical Triple System”, The Astronomical Journal
  • Martioli, E., Colón, K. D., Angerhausen, D., et al., 2018, “A survey of eight hot Jupiters in secondary eclipse using WIRCam at CFHT”, Monthly Notices of the Royal Astronomical Society, 474, 4264
  • Labadie-Bartz, J., Chojnowski, S. D., Whelan, D. G., et al., 2018, “Outbursts and Disk Variability in Be Stars”, The Astronomical Journal, 155, 53
  • Oelkers, R. J., Rodriguez, J. E., Stassun, K. G., et al., 2018, “Variability Properties of Four Million Sources in the TESS Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey”, The Astronomical Journal, 155, 39
  • Ansdell, M., Oelkers, R. J., Rodriguez, J. E., et al., 2018, “Identification of Young Stellar Variables with KELT for K2 II: The Upper Scorpius Association”, Monthly Notices of the Royal Astronomical Society, 473, 1231