The search for habitable planets beyond our solar system has often felt like a pursuit constrained by physics as much as by technology. Stars are colossal furnaces of light that overwhelm their surroundings, making the faint glow of orbiting planets nearly invisible. For decades, astronomers have been developing ways to sidestep this barrier, from watching for subtle dips in starlight as planets pass in front, to measuring the gravitational tug of unseen companions. Yet all of these indirect methods share the same limitation: they cannot directly show us another Earth. They cannot reveal a planet lit by its own reflected or emitted light, hanging apart from its star. To capture such an image requires separating the two sources in space and blocking the blinding glare of the star. That goal has always been presented as requiring telescopes so large and so complex that their construction was placed somewhere far in the future. A new study challenges that assumption, putting forward an idea that is both startlingly simple and technically achievable. Instead of building a giant circular telescope, the researchers propose a rectangular one. By stretching the mirror into a long, thin strip twenty meters in length and one meter in width, the required resolution can be achieved with a design that could fit into today’s rockets and use technology that already exists.
The team, led by Heidi Jo Newberg at Rensselaer Polytechnic Institute, argues that a rectangular telescope working in the infrared could accomplish what larger and more ambitious designs have only promised. Their calculations show that such an instrument could discover around eleven potentially habitable planets within a year of operation and around twenty seven within three and a half years. These would not be distant worlds hundreds of light years away, but nearby neighbors less than ten parsecs from Earth, close enough that in principle they could one day be visited by robotic probes. More importantly, the telescope would be capable of examining their atmospheres, detecting ozone and other gases that might signal biological activity. In effect, the rectangular telescope could deliver the very outcome that NASA’s proposed Habitable Worlds Observatory is being designed for, but with a fraction of the complexity.
The logic behind the design is rooted in the physics of light. To resolve Earth as a separate point of light from the Sun at a distance of ten parsecs, a telescope needs an angular resolution of 0.1 arcseconds at a wavelength of around ten microns. That wavelength is chosen because Earth radiates most strongly there, while the Sun’s brightness is reduced to about one million times greater instead of ten billion times greater as in visible light. The diffraction limit equation shows that achieving this resolution at ten microns requires an aperture with a length scale of about twenty one meters. A circular mirror that large is beyond current engineering capabilities. It would be almost impossible to launch and deploy. Even the James Webb Space Telescope, at 6.5 meters, required two decades of development, intricate folding segments, and one of the most complex deployments in aerospace history. Scaling that up to twenty meters has been considered impractical. But the diffraction limit only requires one long dimension to be large. By stretching a mirror into a strip twenty meters long but only one meter wide, the necessary resolution can be achieved in one direction. By rotating the telescope ninety degrees between exposures, exoplanets can be resolved in any orientation around their stars. What at first seems like an inelegant workaround becomes, in this context, an elegant solution.
The study builds on experience with diffractive instruments called Dittoscopes, which use gratings to achieve high angular resolution. In earlier work, the authors showed that such designs could detect a handful of exoplanets over a seven year mission. But they realized that the essential breakthrough was not the grating, it was the shape. Mirrors with a high aspect ratio offered the same resolution advantage without the need for difficult spectrographs. Recasting the idea into a rectangular mirror simplified everything. Using segments similar to those already employed in JWST, the mirror could be assembled in two ten meter halves, folded for launch, and then unfolded in space. The secondary mirror, about 2.3 by 1 meters, would sit offset to avoid blocking the primary. A sunshield would provide cooling, and the entire observatory could be stationed at the stable L2 point, just like JWST. In fact, the folded spacecraft would be smaller than JWST’s payload, potentially fitting into a Falcon Heavy. This stands in sharp contrast to proposals like LUVOIR or HabEx, which require either enormous monolithic mirrors or precision flying starshades tens of thousands of kilometers away.
Simulations carried out by the team show how powerful the rectangular design could be. Using a catalog of nearby stars, they simulated thousands of habitable zone planets and then tested which could be detected with the telescope. For a sample of fifteen Sun-like stars within eight parsecs, a ten day exposure on each star yielded around eleven habitable planets. For a larger set of forty six stars within ten parsecs, about twenty seven habitable planets could be detected in 1.3 years of exposure time. The telescope would preferentially find planets with temperatures and sizes close to Earth, because those are brightest at ten microns and sit in the right range of separation from their stars. The design’s sweet spot, in other words, aligns with the very targets astronomers most want to find.
Detection is only the first step. The ability to probe the atmospheres of these planets is what transforms the telescope from a survey tool into a potential life finder. The study shows that with a few extra days of observation per planet, the telescope could detect the characteristic absorption band of ozone at 9.6 microns. On Earth, ozone is produced from oxygen released by photosynthesis. While it is true that oxygen can exist through non-biological processes, sustained levels in the atmosphere of a stable planet orbiting a Sun-like star would strongly suggest the presence of life. Thus the rectangular telescope could not only find dozens of Earth-like worlds but also test them for biosignatures. In practical terms, this means humanity could know within a decade whether any nearby planets are alive.
Comparisons with square or circular mirrors of equivalent collecting area highlight the advantage. A square telescope with a diameter of 4.47 meters would gather the same light but would lack the resolution. Its diffraction limit would be 0.46 arcseconds, meaning it could not separate planets closer than 0.23 arcseconds from their stars. The majority of nearby Earth-like planets fall within that distance, making them undetectable. In simulations, such a design only detected a handful of Earth analogs, far short of the twenty five target set by NASA for the Habitable Worlds Observatory. The rectangular mirror, by contrast, comfortably exceeded that benchmark. The conclusion is clear: shape matters more than size.
The paper also discusses noise sources that could complicate detection, such as zodiacal dust within our own solar system and around other stars. These create a background glow that adds to the challenge. By assuming reasonable levels of dust brightness, the researchers calculated that the rectangular telescope could still succeed. Even if exozodiacal light is ten times brighter than in our system, lengthier exposures could recover the full planet yield. The primary limitation is not feasibility but mission duration. A three and a half year campaign would suffice to meet the goals. Given that JWST is planned for at least a ten year mission, such a timescale is well within precedent.
The technical components are also within reach. The required detectors are superconducting single photon devices such as transition edge sensors, nanowire detectors, or kinetic inductance detectors. These technologies have matured rapidly and can deliver the sensitivity needed. The coronagraph envisioned, an achromatic interfero coronagraph, is already developed to the necessary level, capable of suppressing starlight by orders of magnitude while allowing planetary light through. The mirror segments would be scaled-up versions of JWST’s beryllium hexagons. No unprecedented materials, no untested folding schemes, and no unproven propulsion would be required. That point is crucial, because past mission concepts have faltered when their technological requirements outpaced what could reasonably be built. Here the path is direct.
What this means for the broader field is significant. NASA has been weighing designs for the Habitable Worlds Observatory, aware that each step beyond JWST introduces steep risks. The National Academies have set the direct detection of twenty five Earth-like exoplanets as a central goal for astrophysics. Achieving that has been assumed to require large circular telescopes of six meters or more, with extreme coronagraphs or giant starshades. The new rectangular concept undercuts that assumption. It suggests that the same science can be accomplished with a design not much more demanding than JWST itself. If correct, it means that the discovery of habitable worlds and potential biosignatures could happen much sooner than expected. The timeline for a true Earth 2.0 might compress from the latter half of the century to the next decade.
The idea is not without its challenges. A twenty meter long mirror, even if narrow, would need precise alignment and stability. Rotating it to capture planets in different orientations would add complexity. The coronagraph must maintain path length corrections to high precision. Yet compared to the requirements of flying a starshade tens of thousands of kilometers away, or aligning multiple spacecraft to molecular tolerances, these are modest. The authors acknowledge that further engineering studies are needed but emphasize that no insurmountable hurdles stand in the way.
The implications extend beyond exoplanets. A rectangular telescope optimized for infrared could also be adapted for other wavelengths. At visible wavelengths around 500 nanometers, the same twenty meter mirror would resolve down to 0.005 arcseconds, enough to distinguish Earth-like planets out to two hundred parsecs. That is twenty times farther than the infrared case. The stability requirements would be harsher, but the possibility illustrates how a simple change in mirror geometry can unlock new regimes of discovery. For now, though, the most compelling case remains in the infrared, where habitable planets glow brightest and the contrast with their stars is least severe.
Taken as a whole, the study reframes the search for life beyond Earth. It demonstrates that by abandoning the assumption of circular mirrors, astronomers may already have the tools needed to answer the question. The telescope described is not hypothetical science fiction. It could be built, launched, and operated with today’s rockets and today’s detectors. In a field where proposed observatories often balloon to scales that rival national budgets and multi-decade timelines, the rectangular telescope is almost refreshingly practical. The question becomes less about whether it can be done and more about whether the will exists to pursue it.
The scientific payoff would be extraordinary. A catalog of dozens of Earth-like planets within our immediate galactic neighborhood, each with measured atmospheres, would transform not only astrophysics but humanity’s view of itself. If one or more of those atmospheres showed ozone or other biosignatures, the impact would reverberate across every domain of human thought. It would mean that life is not unique to Earth, that the conditions for biology arise wherever the physics and chemistry allow, and that the universe is populated with living worlds. Even a null result, finding habitable planets but no signs of life, would be profound. It would highlight the rarity of Earth and raise urgent questions about why life took hold here but perhaps nowhere else nearby.
What Newberg and her colleagues have offered is a pathway to that knowledge that avoids many of the dead ends of earlier designs. Their paper is careful, rooted in simulations and physics, but its implications are bold. A strip of mirror twenty meters long and a meter wide, floating at L2 and peering into the infrared, could be the machine that finally answers one of the oldest questions of all. It could show us, directly, whether Earth has company. For decades, the phrase Earth 2.0 has been a slogan more than a plan. The rectangular telescope concept suggests it might soon be a reality.
Source:
Newberg, H. J., Swordy, L., Barry, R. K., Cousins, M., Nish, K., Rickborn, S., & Todeasa, S. (2025). The case for a rectangular format space telescope for finding exoplanets. Frontiers in Astronomy and Space Sciences, 12, 1441984. https://doi.org/10.3389/fspas.2025.1441984
