Astronomers are rethinking one of their oldest tools: the telescope’s mirror.
A new study led by Dr. Heidi Newberg of Rensselaer Polytechnic Institute proposes an unorthodox but remarkably efficient design for the next generation of space telescopes: a long, narrow rectangular mirror, rather than the traditional circular kind. Their research, published September 1 in Frontiers in Astronomy and Space Sciences, suggests this change in shape could make it dramatically easier—not to mention cheaper—to detect habitable Earth-like planets around nearby stars.
“We show that it is possible to find nearby, Earth-like planets orbiting sun-like stars with a telescope that is about the same size as the James Webb Space Telescope,” wrote Newberg in an editorial accompanying the paper, “with a mirror that is a one by 20 meter rectangle instead of a circle 6.5 meters in diameter.”
The Exoplanet Imaging Challenge
Finding another Earth is the holy grail of modern astronomy. NASA’s upcoming Habitable Worlds Observatory (HWO) is specifically designed for that mission. But seeing an Earth-sized planet orbiting a star tens of light-years away is like trying to spot a firefly next to a lamp from across the country.
The main challenge is angular resolution: the ability to distinguish two close objects. In this case, a faint planet and its overwhelmingly bright host star. At infrared wavelengths optimal for detecting water vapor and oxygen, even NASA’s $10-billion James Webb Space Telescope (JWST) falls short. To resolve an Earth-like planet at a distance of 30 light-years, scientists estimate you’d need a mirror around 20 meters wide.
That’s triple the diameter of JWST. And building and launching such a vast circular mirror into space is, for now, out of reach.
A Long Mirror’s Advantage
Instead of scaling up a circular mirror, Newberg and her team propose stretching it. They designed a mirror 20 meters long and just one meter wide. This slim, high-aspect-ratio rectangle would focus light more narrowly in one direction, giving it the angular resolution needed to separate a planet from its star—without ballooning the cost and complexity of a full 20-meter circular mirror.
Operating at that wavelength, the rectangular mirror would match JWST’s sensitivity, but surpass it in resolving power. All with a collecting area slightly smaller than JWST’s.
There is a catch: the orientation of the mirror matters. Because its sharpest resolution is along its long axis, the telescope would need to rotate to image planets at different positions around their stars. But the researchers argue that just two exposures, taken at right angles, would be enough to spot most exoplanets.
Less Mirror, More Power
The rectangular design is potentially more efficient than any of the leading alternatives. In simulations of star systems within 10 parsecs (about 32.6 light-years), the team found that their telescope could detect 27 Earth-like planets in the habitable zone with just 10 days of exposure per star.
“If there is about one Earth-like planet orbiting the average sun-like star,” Newberg said, as per Space.com, “then we would find around 30 promising planets.”
Their calculations assume modest instrumentation already developed for JWST, such as the Mid-Infrared Instrument (MIRI), and a coronagraph capable of blocking out starlight. No groundbreaking new tech required. Even the cooling system and mirror deployment could borrow from JWST’s blueprint.
And the design would fit—quite literally—within the capabilities of today’s rockets. A folded version of the rectangular mirror system could possibly ride aboard a Falcon Heavy.
Could We Detect Life?
Identifying Earth-sized planets is just the first step. The real prize would be detecting signs of life in their atmospheres. And here, too, the rectangular telescope shines.
The study estimates that, after discovery, follow-up observations could detect ozone—a proxy for atmospheric oxygen and, by extension, potential photosynthesis—in about a dozen planets over the course of a year. A slightly longer mission of 3.5 years could achieve the Habitable Worlds Observatory’s primary goal: detecting and characterizing 25 potentially habitable exoplanets.
“While our design will need further engineering and optimization before its capabilities are assured,” Newberg wrote, “there are no obvious requirements that need intense technological development, as is the case for other leading ideas.”
That includes interferometry, the complex technique of combining light from multiple spacecraft with nanometer precision. It also beats out circular telescopes of similar area, which the team found were incapable of resolving the exoplanets due to a larger diffraction limit. A square telescope with the same collecting area could only detect 5% of Earth-analog planets in the simulation.
Why This Matters Now
The search for habitable exoplanets is among the top priorities in the National Academies’ Decadal Survey for Astronomy and Astrophysics. And with telescopes like JWST and the Vera C. Rubin Observatory already revolutionizing our view of the cosmos, the astronomical community is actively debating what the next flagship mission should look like.
Most concepts on the table—including LUVOIR and HabEx—require either massive engineering leaps, such as ultra-precise interferometry or vast multi-mirror deployments, or narrow capabilities limited to visible and UV light. The rectangular concept, by contrast, offers a relatively low-tech, high-payoff route to imaging another Earth.
And perhaps most importantly, it answers the question: Can we detect life within our cosmic neighborhood using tools we can build soon?
The answer, it seems, may be yes. All it takes is a different shape.
