A new study suggests a new telescope design could help scientists find Earth-like planets orbiting sun-like stars. Unlike traditional circular telescopes, this innovative concept proposes a rectangular mirror, offering a simpler and cheaper way to search for habitable worlds.
Heidi Newberg, a professor of astrophysics at Rensselaer Polytechnic Institute, explains the idea in a statement. “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 [JWST], operating at roughly the same infrared wavelength as JWST, with a mirror that is a one by 20 meter [65.6 by 3.3 foot] rectangle instead of a circle 6.5 meters [21.3 feet] in diameter.”
The goal is to detect planets with water vapor in their atmospheres, a key sign of potential habitability. To do this, the telescope would focus on light with a wavelength of 10 microns, where water vapor emits strongly. At this infrared wavelength, planets are less faint compared to their stars making them easier to detect. The JWST, with its 21.3-foot (6.5-meter) circular mirror, is too small to resolve Earth-sized planets in the habitable zones of sun-like stars. A circular telescope would need a massive 65.6-foot (20-meter) mirror to achieve the necessary resolution, but building and launching such a giant would be costly and complex.
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Another option, using many small telescopes as an interferometer, is also challenging due to the need for precise alignment. Newberg’s team proposes a rectangular mirror, 65.6 feet by 3.3 feet (20 meters by 1 meter), as a solution. This design has a smaller surface area than the JWST’s mirror but focuses all its light-collecting power in the direction needed to spot a planet. By aligning the telescope’s long side with the planet’s position relative to its star, and rotating it if needed, the design maximizes efficiency. The study, published on September 1, 2025, in Frontiers in Astronomy and Space Sciences, highlights the telescope’s potential.
Newberg writes, “We show that this design can, in principle, find half of all existing Earth-like planets orbiting sun-like stars within 30 light years in less than three years.” With about 69 sun-like stars and nearly 300 smaller M dwarf stars within 32.6 light-years, the telescope could discover around 30 promising planets if each sun-like star hosts one Earth-like world.
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