A new study proposes that building a rectangular-shaped telescope, instead of the traditional circular design, could dramatically improve our chances of finding habitable Earth-like planets orbiting nearby stars.

The Challenge of Spotting Another Earth

Finding an exoplanet that resembles Earth is notoriously difficult. Stars are millions to billions of times brighter than the planets orbiting them, making the faint planetary light nearly impossible to distinguish.

Liquid water is considered essential for life as we know it, and the best candidates for habitable planets are those orbiting sun-like stars within about 30 light-years. These stars are stable enough to allow complex life to evolve, and they are close enough that spacecraft observations may be feasible within a human lifetime.

But the technical challenges are immense. To separate the light of a star from that of an Earth-like planet at these distances, a telescope must collect infrared light around 10 microns in wavelength—requiring an aperture at least 20 meters across. By comparison, NASA’s James Webb Space Telescope (JWST) has a mirror only 6.5 meters in diameter and was already an extraordinary engineering feat.

Why Current Approaches Fall Short

Scientists have considered several workarounds to bypass the need for an impossibly large space telescope:

• Multiple Small Telescopes: Acting in concert, they could mimic one giant telescope. However, maintaining molecular-level precision between spacecraft is beyond today’s capabilities.
• Shorter Wavelength Observations: While reducing telescope size, these make it nearly impossible to block overwhelming starlight.
• Starshades: Massive screens positioned thousands of miles from a telescope could block starlight, but would require extreme precision and vast amounts of fuel to reposition.

So far, none of these options seem practical.

A Rectangular Alternative

The new research suggests a simpler solution: a rectangular mirror about 1 by 20 meters in size. Operating in the same infrared range as JWST, this design could separate starlight from a nearby exoplanet along the mirror’s long axis. By rotating the telescope, astronomers could search for planets in any orbital orientation.

Modeling indicates that such a telescope could identify half of all Earth-like planets orbiting sun-like stars within 30 light-years in under three years. This would represent a major leap forward, without requiring breakthroughs in spacecraft positioning or exotic new technologies.

Toward Identifying Earth 2.0

If every sun-like star hosts roughly one Earth-like planet, this telescope design could uncover about 30 promising worlds in our stellar neighborhood. Further studies could analyze their atmospheres for biosignatures such as oxygen from photosynthesis.

For the most compelling candidates, future missions could even send robotic probes to return images of their surfaces—bringing humanity closer than ever to finding Earth 2.0.

Key Takeaways

• Detecting Earth-like exoplanets requires unprecedented telescope resolution and starlight suppression.
• Traditional approaches—giant circular mirrors, multiple spacecraft arrays, or starshades—pose extreme technical challenges.
• A rectangular telescope (1 × 20 meters) offers a feasible alternative, operating at the same infrared wavelength as JWST.
• This design could identify ~30 Earth-like planets within 30 light-years in less than three years.
• Follow-up observations may reveal signs of life and guide future interstellar probes.

Original Publication
Authors: Heidi Jo Newberg, Leaf Swordy, Richard K. Barry, Marina Cousins, Kerrigan Nish, Sarah Rickborn and Sebastian Todeasa.
Journal: Frontiers in Astronomy and Space Sciences
DOI: 10.3389/fspas.2025.1441984
Method of Research: Case study
Subject of Research: Not applicable
Article Title: The Case for a Rectangular Format Space Telescope for Finding Exoplanets
Article Publication Date: 1-Sep-2025
COI Statement: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Original Source: https://frontiersin.org/news/2025/09/01/rectangle-telescope-finding-habitable-planets

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