A new Congressionally-mandated study, co-authored by University of Maryland Astronomy Assistant Professor Eliza Kempton, says that NASA should lead a large “direct imaging” mission—an advanced space telescope—capable of studying distant Earth-like planets and whether they might harbor life.
The report by the National Academies of Sciences, Engineering, and Medicine, says developing a direct imaging capability will require large financial investments and a long time scale to see results, but the effort will foster the scientific community and technological capacity needed to find and understand myriad distant worlds.
“My expertise is primarily in the theory of exoplanet atmospheres, with a focus on small planets,” said Kempton. “A big goal of the report was to make a roadmap for the next decade plus, and we decided we didn’t want to step away from being very ambitious. A primary goal is to characterize planets that can and do bear life—a push toward finding the next Earth.”
Within the past decade, astronomers have opened a new frontier in space exploration with the discovery of thousands of exoplanets— planets orbiting stars outside our solar system. However, Kempton and the other committee members say in the report that our current knowledge of exoplanets (planets outside our solar system) is substantially incomplete.
To search for evidence of past and present life elsewhere in the universe, the research community will need a comprehensive approach to studying habitability in exoplanets using both theory and observations, according to the report.
To be able to detect a solar system analogous to our own Earth-sun system, they recommend using instruments that can directly image exoplanets by using techniques to block the light emitted by parent stars. At present, most exoplanet observations rely on indirect methods, such as measuring changes in the light from a planet’s host star during the planet’s orbital cycle.
“Planning is already underway for the large next-generation telescopes that will follow the Webb Telescope,” Kempton explained, referring to possible successors to NASA’s highly anticipated James Webb Space Telescope mission, scheduled for launch in 2021. “Of these proposed missions, three have exoplanet science and habitable exoplanets among their key goals. Two of those are large direct imaging missions that would be able to take pictures of Earth-like planets orbiting near their host stars”
In her research, Kempton uses theory to predict what astronomers should expect to observe from exoplanets with specific atmospheric compositions—especially those that are slightly larger than Earth, often referred to as super-Earths. In 2010, she co-authored a paper in the journal Nature that described the first observation of a super-Earth atmosphere.
In the National Academies report, she and her colleagues note that ground-based astronomy—enabled by two U.S.-led telescopes—will also play a pivotal role. The Giant Magellan Telescope being built in Chile and the proposed Thirty Meter Telescope would enable profound advances in the imaging and spectroscopy of entire planetary systems. These may also be able to detect molecular oxygen in the atmosphere of Earth-like planets orbiting nearby small stars, the report said.
The committee said that NASA’s Wide Field Infrared Survey Telescope (WFIRST), the large space-based mission that received the highest priority in the Academies' 2010 decadal survey, will play two extremely valuable roles: first, it will permit a survey of planets farther from their stars than those surveyed by NASA’s Kepler spacecraft and other missions. Second, it will enable a large direct imaging mission. In addition to such forward-looking plans, Kempton noted that the Webb Telescope will play a significant role in the effort as soon as it is launched.
“The scientific returns from these missions will be significant. We’ll be getting data from the Webb Telescope’s Early Release Science program basically right away,” Kempton explained. “I’ve been waiting my whole career to measure the composition of small planets’ atmospheres. We’ll have those data very soon, so it’s a very exciting time.”