UMD Astronomer Co-authors National Academies Report Calling for Large Mission to Study Earth-like Exoplanets

UMD Astronomy Assistant Professor Eliza Kempton co-authored report that outlines a long-term strategy to explore distant planets that might harbor life

Within the past decade, astronomers have discovered thousands of planets orbiting stars outside our solar system. Ranging in size from smaller than Earth’s moon to several times larger than Jupiter, these planets—known as extrasolar planets or exoplanets—represent a new frontier in space exploration.

Many questions about exoplanets and their host stars remain unanswered. For example, do these planetary systems resemble our solar system, or have they taken on a wide variety of sizes and structures? Do any of these exoplanets have the right conditions to support life? If so, has life already evolved there?

To answer these and other questions about distant planetary systems, a new congressionally mandated report by the National Academies of Sciences, Engineering, and Medicine, co-authored by University of Maryland Astronomy Assistant Professor Eliza Kempton, recommended that NASA should lead a large, long-term direct imaging mission. 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.

To gain the information required to tackle complex questions about exoplanets, the report suggested that the future mission should be centered on an advanced space telescope capable of directly imaging smaller, Earth-like exoplanets that orbit stars similar to the sun.

“My expertise is primarily in the theory of exoplanet atmospheres, with a focus on small planets,” Kempton said. “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.”

A recent addition to UMD’s faculty, Kempton was previously an assistant professor of physics at Grinnell College in Grinnell, Iowa. In her research, she 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, Kempton co-authored a paper in the journal Nature that described the first observation of a super-Earth atmosphere. She also works with observational astronomers to interpret their results based on theoretical predictions. Since completing her Ph.D. at Harvard in 2009, she has served on several NASA and National Science Foundation advisory committees, helping to determine exoplanet research priorities for the Hubble Space Telescope and other observing facilities.

Kempton and the other committee members who authored the National Academies report identified two overarching goals in exoplanet research:

• To understand the formation and evolution of planetary systems as products of star formation and to characterize the diversity of their architectures, composition and environments; and
• To learn enough about exoplanets to identify potentially habitable environments and to search for scientific evidence of life on worlds orbiting other stars.

Based on these goals, the committee found that current knowledge of planets outside the 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.

The committee recognized that developing a direct imaging capability will require large financial investments over more than a decade to see results. To detect a planetary system analogous to our own, the report recommended using instruments that enable direct imaging of an exoplanet by blocking the light emitted by the parent star.

“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 addition, ground-based astronomy—enabled by two U.S.-led telescopes—will also play a pivotal role, the report said. The Giant Magellan Telescope (GMT) being built in Chile and the proposed Thirty Meter Telescope (TMT) would enable profound advances in the imaging and spectroscopy of entire planetary systems. They may also be able to detect molecular oxygen in the atmosphere of Earth-like planets orbiting nearby small stars, the report said.

The report 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.”

VIDEO: Exoplanet Science Strategy (The National Academies of Sciences, Engineering, and Medicine):

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This release was adapted from text provided by the National Academies of Sciences, Engineering, and Medicine. To view the original release, including additional technical information and a full listing of the committee members, please visit: http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=25187

Media Relations Contact: Matthew Wright, 301-405-9267, mewright@umd.edu

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