Advancing the search for Earth-like planets should be a three stage process spanning the next 15-20 years, according to the final report of a NASA and National Science Foundation (NSF) Extreme Precision Radial Velocity (EPRV) Working Group.
One of the report’s three editors, Jonathan Crass, research assistant professor in the Department of Physics, said the working group brought together many world experts the EPRV technique to support the science of ultra-precise measurements—which provide information on mass, orbit, and demographics—of exoplanets orbiting sun-like stars in the galaxy. The group has been meeting both in-person and virtually since 2019 and finished its report in July 2021.
Researchers have found it challenging to overcome the effects that limit existing astronomical instruments and prevent them from detecting potentially habitable planets. Effects of instrument stability, the changing surface of the star which planets orbit or contamination from the earth’s atmosphere can all overwhelm minute exoplanet signals.
“When searching for exoplanets using radial velocity instruments, we are trying to detect tiny changes in the wavelength of light coming from the planet's host star due to the orbit of a planet. The effect is incredibly small—a shift of only a few atoms on our detectors—and so any other effects can impact that signal,” Crass said. “The EPRV Working Group has developed a roadmap which allows the science community to focus its efforts towards addressing the key items which limit our capabilities today.”
The plan outlines 11 different findings that include suggestions from advancing the understanding of stellar physics and its impact on radial velocity measurements, to investing in new technologies, to retaining enough early-career scientists to lead the program.
Given the length of time for the initiative, the first stage will be to coordinate activities during the next five years to determine how feasible it is to correct the effects of the stars which exoplanets orbit.
The second stage will begin once researchers are confident that stellar effects can be worked through. In this stage, Crass said, researchers will spend five to ten years doing a precursor survey of stars they have targeted as having potential to host Earth-like planets. For this step, scientists will use existing instruments, like iLocater, a first-of-its kind spectrometer, that were identified during the first stage of the program. Investment will also be focused in improving instrument performance and telluric contamination—the way the earth’s atmosphere can interfere with astronomical observations.
Finally, once those stages are complete, the group recommends that a full EPRV survey be completed, which will require developing new instruments and building new telescope facilities around the globe.
“The work of the EPRV Working Group in the past two years has delivered a pathway for overcoming the current obstacles and developing the tools and instruments needed to be able to detect other planets like Earth. Providing this capability will support future science missions to directly image these planets, inform our understanding of planet formation, and understand how common planets like our own Earth really are.”
In addition to Crass, the other two editors of the report included Scott Gaudi, of The Ohio State University, and Stephanie Leifer, of the Jet Propulsion Laboratory at the California Institute of Technology. About 60 astrophysicists were part of the EPRV Working Group.