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Experts urge NASA to build huge new space telescope to look at alien Earths

Alan Boyle
An artist’s conception shows a planet-hunting space telescope accompanied by an umbrella-like starshade that blocks the glare of the planet’s parent star. (NASA / JPL Illustration)

NASA should add a large, technologically advanced space telescope to its lineup to capture direct images of Earthlike planets beyond our solar system, astronomers say in a congressionally mandated report issued today.

The report, published under the aegis of the National Academies of Sciences, Engineering and Medicine, also calls on the National Science Foundation to invest in the next-generation Giant Magellan Telescope and the Thirty Meter Telescope.

The GMT is being built in Chile, with completion set for 2025. The TMT is also due to go into service in the mid-2020s, although the current plan to build it on the top of Hawaii’s Mauna Kea volcano has run into controversy.

Authors of the report, led by Harvard’s David Charbonneau and Ohio State University’s B. Scott Gaudi, voiced support for two space telescopes already in the works — NASA’s James Webb Space Telescope and the Wide-Field Infrared Survey Telescope, or WFIRST. They also said NASA’s recently launched Transiting Exoplanet Survey Satellite, or TESS, would provide valuable information about Earth-size exoplanets as well.

But the report makes clear that the search for alien planets will have to focus down on direct images of planets, as well as detailed analysis of exoplanet atmospheres, in order to address questions about the existence of life beyond our solar system.

“We’re alive at a very special moment in human history, where we don’t have to just wonder anymore,” Charbonneau told reporters. “If we choose, and the report presents a path to achieve this … we could learn the answer to that question. We could figure out whether or not there’s life on planets orbiting other stars in the next 20 years.”

So far, the search for alien planets has employed two primary methods: the radial velocity method, which involves looking for faint gravitational wobbles in the motions of stars with planets; and the transiting method, which looks for faint dips in starlight as a planet passes over the disk of its parent star.

Those methods already have started to yield information about the atmospheres of alien planets, and to determine the precise masses of Earthlike planets, the report says NASA and NSF should establish a strategic initiative to measure “extremely precise radial velocities.”

But both methods face fundamental limits. For that reason, direct imaging of planets looms as the next frontier in the exoplanet search. That will require the development of high-precision coronagraphs or starshades to block out the glare of Earthlike planets’ parent stars.

“Due to focused investments by NASA and other agencies, we are now within shouting distance of having that technology in hand, where we can actually detect that ‘pale blue dot,’ in the words of Carl Sagan, and characterize its atmosphere,” Gaudi said.

At least two planet-hunting space telescopes have been proposed: the Habitable Exoplanet Observatory, or HabEX; and the Large UV/Optical/IR Surveyor, or LUVOIR.

The report holds off from recommending either proposed telescope. Such recommendations will come instead from a decadal survey during which panels of astronomers will prioritize the top scientific questions for the 2020-2030 time frame. The Astro 2020 survey is due to be conducted over the next couple of years under the guidance of the National Academies.

Watch a replay of today’s briefing on the report, titled “Exoplanet Science Strategy”:

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