Skip to main content
Research Areas

Exoplanets and
Brown Dwarfs

Questions and Objectives

  • How do planets form? Are there multiple mechanisms of formation? In what circumstances do they operate?
  • What is the frequency of planets as a function of planet mass, primary mass, separation, age, metallicity, and star-forming environment? What does this frequency tell us about the process of planet formation?
  • How often do planetary systems have architectures similar to the Solar System? Is the Solar System's configuration of giant planets at and beyond 5 AU and terrestrial planets within 5 AU the norm, rare, or practically unique?
  • How can we confidently identify which planetary systems that formed via disk migration, planet-planet scattering, or other forms of dynamical evolution?
  • How common are rocky planets? How often are they habitable?
  • What is the smallest mass of brown dwarfs? How do brown dwarfs form?
  • Do planets form around brown dwarfs? How does planet formation compare between stars and brown dwarfs?
  • Can we use the coolest brown dwarfs to test models of planetary atmospheres?

Discoveries and Milestones

  • Alex Wolszczan discovered the first known planet outside the solar system.
  • Steinn Sigurdsson used the Hubble Space Telescope to detect a white dwarf orbiting a pulsar, which demonstrated that the timing anomalies from the pulsar were caused by a planetary companion.
  • Kevin Luhman has discovered some of the least massive known brown dwarfs (~5 MJup).
  • Using the Keck, Lick, and Hobby-Eberly observatories, Jason Wright and his collaborators have discovered many systems with multiple giant planets.
  • Kevin Luhman discovered a candidate for the coolest body directly observed outside the solar system, with a temperature similar to that of Earth.
  • Suvrath Mahadevan has conducted successful on-site tests of an infrared laser frequency comb at the Hobby-Eberly Telescope with the Pathfinder spectrograph.
  • Rebekah Dawson is studying the formation, dynamics, and stability of planetary systems.
  • Kevin Luhman is continuing to search for substellar companions to stars in the solar neighborhood using infrared images from the Spitzer Space Telescope.
  • The Habitable Zone Planet Finder, a facility instrument at the Hobby-Eberly Telescope built by a group led by Suvrath Mahadevan at Penn State, is surveying nearby, cool stars for Earth-mass planets.
  • The NEID spectrograph, a facility instrument at the 3.5m WIYN observatory built by a group led by Suvrath Mahadevan at Penn State, is surveying neary, Sun-like stars for rocky planets. 
  • Eric Ford and the NEID team are analyzing NEID observations of the Sun to develop and test new methods for improving the sensitivity of Doppler planet surveys in the presence of stellar variability.  
  • Eric Feigelson is developing novel statistical methods to improve the sensitivity of searches for small transiting planets. 

Student Highlights

  • Jacob Luhn, working with Jason Wright and Fabienne Bastien, discovered several new planets

    orbiting evolved stars a bit more massive than the sun.