Astronomers are urging NASA to build a huge space telescope to see Earth-like worlds outside our solar system

• Astronomers are asking NASA to build a huge space telescope that could image Earth-like exoplanets.
• That's just one recommendation in a new decadal report that sets the stage for 2020s astronomy.
• NASA doesn't yet have technology to see the faint glow of Earth-like exoplanets.

NASA is about to launch its new flagship space observatory, the James Webb Space Telescope, which can peer so deep into the cosmos that it may see the afterglow of the Big Bang. But some astronomers are already calling for the next big space telescope – one that could take photos of Earth-like planets orbiting other stars.

The National Academies of Sciences, Engineering, and Medicine published its new Decadal Survey on Astronomy and Astrophysics on Thursday. Astronomers look to this report to define each decade in space, since the survey guides NASA and the National Science Foundation (NSF). This time, the report looks beyond the next 10 years, recommending that NASA and the NSF spend the 2020s investing in a series of telescopes that would change our understanding of the universe in decades that follow.

The most ambitious proposal in the report suggests that NASA build an $11 billion space telescope that can peer across the universe in optical, infrared, and ultraviolet light. Such a telescope would have a 6-meter mirror and the ability to dull distant starlight, thereby enabling it to spot Earth-like worlds orbiting other stars. The proposal calls for this observatory to launch in the first half of the 2040s.

The telescope would then be poised to take the first photos of planets beyond our solar system – called exoplanets – where life may thrive. According to Vanderbilt University astronomer Keivan Stassun, those images would resemble the famous "Pale Blue Dot" photo of Earth, which NASA's Voyager spacecraft snapped in 1990 after it zipped past Neptune.

"We'll be able to understand the makeup of that Earth. We'll understand what's on its surface. We'll be able to measure the contents of the atmosphere that it holds, if it has an atmosphere. That's science fiction becoming science fact," Stassun, who is on the steering committee for the decadal survey, told Insider.

To study those worlds, this future space telescope would need to blot out the shine of distant stars, since the light of small planets is about 10 billion times fainter than starlight. NASA doesn't currently have the technology to do that.

"We have to be able to suppress that starlight by a factor of 10 million times or more, while at the same time preserving the faint little firefly glow of the planet itself," Stassun said. "We believe we can get there, but that's going to take a long time. We're going to have to demonstrate in the laboratory. We're going to have to probably fly some precursor missions to show that it can work. That's a tall order."

The new report tells NASA and NSF to build, build, build

A space observatory that can image alien worlds may be the most ambitious telescope proposed in the new decadal report, but it's certainly not the only one. The authors said their recommendations would advance three scientific goals: studying habitable worlds beyond our solar system; understanding black holes, dead stars, and the explosive events that create them; and learning how galaxies form and evolve.

But astronomers need better telescopes for those studies, the report says. So it asserts that the NSF's highest priority should be completing its largest land-based telescopes already under construction: the Giant Magellan Telescope in Chile and the Thirty Meter Telescope in Hawai'i. For NASA, the report recommends a new "Great Observatories" program to develop multiple space missions at once, including the ambitious telescope that could see Earth-like worlds.

The decadal survey also recommends expanding Earth's array of radio telescopes, upgrading existing gravitational-wave observatories and building new ones, and developing an observatory that would study microwave radiation left over from the Big Bang.

"As we learned with the James Webb Space Telescope, our ambitious scientific objectives now simply cannot fit neatly within a decadal timeframe," Stassun said.

He added: "There's a large number of things that we are saying we need to start on today."