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?
- Can we find systems that are definitely the result of 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?
- How should we define giant planetary companions and brown dwarf companions, and how do we distinguish between them observationally?
- 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 telescopes, Jason Wright and his collaborators have discovered a substantial number of all known multiplanet systems.
- 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.
- Sara Gettel and Alex Wolszczan are using the radial velocity measurements from the Hobby-Eberly Telescope to search for planets around K giants.
- Matthew Route and Alex Wolszczan are using Arecibo to search for radio emission from free-floating brown dwarfs and giant planetary companions.
- Suvrath Mahadevan and Larry Ramsey are developing and testing the Pathfinder spectrograph, which will be used to search for planets around low-mass stars using infrared radial velocity measurements.
- John Bochanski, Kevin Luhman, and Sonali Shukla are using images from the Hubble Space Telescope to search for young brown dwarfs down to ~3 MJup, providing a better constraint on the minimum mass at which free-floating bodies can form.
- Suvrath Mahadevan is participating in the MARVELS exoplanet survey and the APOGEE H-band radial velocity survey within SDSS-III. He is also participating in the TERMS survey for transiting planets.
- Jason Wright is using the Hobby-Eberly Telescope to track long-period planets around the nearest stars, and to improve its ability to detect very low mass planets.
- Rebekah Dawson, Andrew Shannon, Jonathan Jackson, Mariah MacDonald, and Matthias He are studying the formation, dynamics, and stability of planetary systems.
- Arpita Roy and Suvrath Mahadevan are involved with the commissioning of the PARAS instrument in India and developing data analysis pipeline for first light.
- Genady Pilyavsky and Suvrath Mahadevan are developing a high precision photometric pipeline for the TERMS survey to search for bright transiting exoplanets.
- Kevin Luhman is continuing to search for substellar companions to stars in the solar neighborhood using infrared images from the Spitzer Space Telescope.
- Stephen Redman helped to develop the Pathfinder spectrograph for searching for planetary companions to low-mass stars via radial velocity measurements at infrared wavelengths. He also has produced a new atlas of calibrations of hollow cathode lamps for use in infrared spectroscopy.
- Kamen Todorov discovered a planetary-mass companion to a young brown dwarf using high-resolution images from the Hubble Space Telescope.
- Amanda Morrow used spectra from the Spitzer Space Telescope to show that grain growth in disks -- one of first steps in planet formation -- may occur faster for brown dwarfs than for stars.
- Jacob Luhn, working with Jason Wright and Fabienne Bastien, discovered several new planets and hints of several more orbiting evolved stars a bit more massive than the sun.
James Kasting (Geosciences)
Center for Exoplanets and Habitable Worlds
Penn State Astrobiology Research Center
A detailed description of Mercedes Richards' work related to exoplanets and brown dwarfs