A report by the National Academies of Sciences, Engineering, and Medicine sets the stage for Penn State's Center for Exoplanets and Habitable Worlds to expand its role in NASA's exoplanetary science initiatives
To answer significant questions about planetary systems, such as whether our solar system is a rare phenomenon or if life exists on planets other than Earth, NASA should lead a large direct imaging mission — an advanced space telescope — capable of studying Earth-like exoplanets orbiting stars similar to the sun, says a congressionally mandated report by the National Academies of Sciences, Engineering, and Medicine.
The Hobby-Eberly Telescope — one of the world’s largest optical telescopes and a premier planet-finding facility, conceived by Penn State astronomers. Credit: Penn State
“Penn State astronomers and astrophysicists — especially those in the Center for Exoplanets and Habitable Worlds — are well-positioned to make key contributions toward answering these questions,” said Fabienne Bastien, assistant professor of astronomy and astrophysics at Penn State and a member of the Committee on Exoplanet Science Strategy, which authored the report. “The University’s scientists also have the kind of expertise in designing and building telescopes and other astronomical instrumentation that would be critical to a large direct imaging mission.”
"Over the past decade, Penn State has been a leader in research laying the groundwork for such a mission," said Eric Ford, professor of astronomy and astrophysics, member of the Institute for CyberScience, and director of the Center for Exoplanets and Habitable Worlds (CEHW) at Penn State. "CEHW researchers continue to play important roles in discovering and characterizing exoplanets as well as interpreting observations to better understand the processes of planet formation. By combining our expertise, we can envision how future observatories can best characterize the atmospheres and surface conditions of potentially habitable exoplanets.”
The National Academies' report also outlines the key role that ground-based astronomy will play in studying planet formation and characterizing potentially habitable worlds, and it recommends investment in exoplanet instrumentation as well as the establishment of a strategic initiative in extremely precise radial velocities (EPRVs) to develop methods and facilities for measuring the masses of temperate terrestrial planets orbiting Sun-like stars — all areas in which Penn State is an established leader.
"The recommendation that NASA pursue an EPRV initiative is a direct result of the work that's been coming out of this department," said Bastien. "Penn State hosted the first and third EPRV workshops in 2012 and 2017, and we are currently leading development of two world-class next-generation spectrographs for EPRV. My research on stellar astrophysics as it pertains to exoplanet research is ultimately why I was invited to join the committee. And an increased appreciation, in the general exoplanet community, of the stellar astrophysics challenges to exoplanet detection in radial velocities was one of the major drivers for the committee's recommendation of an EPRV initiative."
For more than 25 years, Penn State scientists have held a leading position in the exoplanetary science community, with multiple groundbreaking discoveries to their credit. In 1992, Alexander Wolszczan (then at Cornell), with Dale Frail of the National Radio Astronomy Observatory, discovered the first planets outside our solar system and thus began the present era of planet hunting. Wolszczan later founded and directed the Center for Exoplanets and Habitable Worlds at Penn State, bringing together scientists from a variety of disciplines across the University to search for, discover, and study new exoplanets.
"A broad range of Penn State’s exoplanet science, and its high international visibility, is intimately related to the decade-long growth of the University's Center for Exoplanets and Habitable Worlds," said Wolszczan, Evan Pugh University Professor of Astronomy and Astrophysics at Penn State. "The Center provides a very well-functioning framework for a variety of research activities, including both the very successful planet-hunting and groundbreaking studies of the known planets and planetary systems."
Also among Penn State's distinctions in exoplanetary science is the 2014 discovery — by an international team of astronomers that included Eric Ford — of the first Earth-size planet orbiting a star in its habitable zone, the region around a star where liquid water might form on the surface of an orbiting planet and thus potentially sustain life. Discovered with NASA's Kepler Space Telescope, that planet — named Kepler-186f — is one of a class known as transiting exoplanets, which pass in front of their host star. Ford and other researchers at the Center for Exoplanets and Habitable Worlds are leaders in interpreting observations of transiting exoplanets, from which much of our current knowledge of exoplanets has been gleaned and on which NASA has focused a sizable portion of its investment in exoplanetary science.
"In the past decade, astronomers have discovered an unexpected abundance of small planets orbiting close to their host star; and this year, NASA launched a new mission — TESS — designed to identify transiting planets around bright, nearby stars," said Ford. "Thanks to strategic investments in EPRV instruments, Penn State astronomers will play an important role in follow-up observations of transiting planet candidates identified by TESS, using upcoming observatories such as the James Webb Space Telescope and eventually an even more ambitious space mission such as HabEx or LUVOIR. Penn State professor Rebekah Dawson serves on the LUVOIR mission concept's Science and Technology Definition Team, which is laying the groundwork for LUVOIR.”
In fact, the University has a distinguished history of pioneering innovations in optical and infrared instrumentation, dating back to 1983 when Larry Ramsey and Daniel Weedman invented the concept for the 10-meter Hobby–Eberly Telescope (HET) — one of the world's largest optical telescopes and a premier planet-finding facility — in which Penn State continues to be a major partner. Ramsey was intensely involved in the design and construction of the HET and has continued to be work on its operation and management. Along with Penn State's Suvrath Mahadevan, Ramsey co-led development of the Habitable Zone Planet Finder (HPF) spectrograph, which was installed on the HET in late 2017 and is now in the process of being commissioned. Mahadevan is currently leading development of the NEID spectrograph, scheduled to be installed on the 3.5-meter WIYN Telescope at Kitt Peak National Observatory in Arizona in 2019. Both the HPF and the NEID, once they are fully operational, will be premier radial velocity instruments for discovering and studying exoplanets.
"Penn State's expertise in EPRVs and astronomical instrumentation is a critical aspect of fulfilling the vision of the future of exoplanet science and charting the path to higher precision in our measurements,” said Mahadevan, associate professor of astronomy and astrophysics at Penn State. Mahadevan is also heavily involved with University's institutional partnership in the Sloan Digital Sky Survey-IV, which, for one of its four scientific programs, is conducting follow-up studies of planet-hosting stars discovered by NASA's Kepler mission.
Additionally, Jason Wright is currently leading the University's partnership in MINERVA — the first U.S. observatory dedicated to exoplanetary science capable of both precise radial velocimetry and transit studies — at the Fred Lawrence Whipple Observatory in Arizona. "With MINERVA, NEID, and HPF, Penn State is leading three of the most innovative and powerful planet-finding instruments in the world," said Wright, associate professor of astronomy and astrophysics at Penn State. "Together, they will provide nearly nightly monitoring of the closest, brightest, and most sun-like stars to find their smallest and most temperate worlds."
"Penn State has developed a tradition of excellence in both space- and ground-based astrophysics over several decades," said Larry Ramsey, Distinguished Senior Scholar, professor of astronomy and astrophysics, and former head of the Department of Astronomy and Astrophysics at Penn State. "And with the establishment of the Center for Exoplanets and Habitable Worlds about a decade ago, we have been able to recruit outstanding young talent in this area, providing a strong base for continued leadership."
Seth Palmer: email@example.com, 814-863-3584