Could this telescope find life on alien worlds?
ExoLife Finder is imagined here as a 35-meter-diameter array of smaller mirrors, supported by a complex structure of wires that perfectly balances so that the elements hold each other up. Its unique design will allow astronomers to combine the light from the mirrors in such a way to block the glare of a star and directly image the faint planets around it. Credit: Image courtesy of LIOM and the Instituto de Astrofísica de Canarias (IAC)
The ExoLife Finder (ELF) looks like no telescope ever built. A spectacular crown of 15 five-meter mirrors perches atop a sprawling metal lattice, resembling petals on a 10-story-tall mechanical flower — more sculpture than observatory. It is a fundamentally new type of telescope, one that its designers say could discover life on Earth-like planets beyond our solar system.
The radical design is the brainchild of astrophysicist Jeff Kuhn of the University of Hawai‘i. For now, it exists only in renderings. To build it, Kuhn and the team he’s assembled must first develop and perfect techniques and technologies never before used in astronomy.
That ring of mirrors, working in sync, would use a cutting-edge technique — the equivalent of stellar noise canceling — to block out the glare of a host star so it can capture images of orbiting worlds. If it works, it could monitor planets, create surface maps, and possibly even detect heat given off by life-forms or their technology.
“For a long time, it was thought that this [technique] required telescopes in space,” says John Mather, the Nobel Prize-winning astrophysicist who led the science team for the James Webb Space Telescope (JWST). “But Kuhn’s team showed that it might not be impossible from the ground.”
The word _might_ is meaningful here. The technical hurdles are high. And in the race to build a telescope that can find a second Earth, there is no shortage of competing ideas. But if the experiment succeeds, it could open the door to a new era of ground-based telescopes — and settle the question of whether we are alone in the universe.
## Seeing other worlds
The first challenge of imaging any exoplanet is resolution — being able to resolve the planet separately from its host star. All telescopes have a fundamental physical limit: the diffraction limit. This defines how sharp an image the telescope can produce, and it’s related to the wavelength of the incoming light and inversely to the size of the mirror. The larger the mirror’s diameter, the smaller the diffraction limit and the finer the details it can resolve.
ELF borrows a concept from radio astronomy called interferometry. It will use many mirrors distributed in an array, and combine their light. With specialized optical equipment to combine the beams, extremely careful calibration, and a lot of math, this technique can produce an image as sharp as if it were taken with a single mirror the same size as the widest point of the array, called the baseline. ELF’s ring of mirrors is 115 feet (35 meters) across, rivaling the aperture of the largest telescope currently under construction, the 39-meter Extremely Large Telescope in Chile, but leaving out the central mirror segments — and the associated price tag.
“[It’s] a great trick. We’ve used it in radio astronomy for a long time,” says SETI pioneer Jill Tarter of the technique, called aperture synthesis. “It’s harder in the optical part of the spectrum,” she notes — it requires more precise control over the beams of light due to the shorter wavelengths of visible light — “but now they can do it.”
But resolution is not the hardest challenge: Astronomers must also suppress the overwhelming light from the host star, so that only the faint reflected light from the planets remains. The smaller the planet, the fainter and more challenging it is to image. So far, the smallest planets we have been able to image are the size of Saturn. Going smaller will require technological advances and the ability to capture scenes with higher contrast.
Direct imaging of exoplanets is possible today using a coronagraph to physically block out the host star’s light. This technique allows us to see large (bright) Jupiter-sized gas giant planets far from their stars; smaller, terrestrial and Earth-like planets remain invisible with current technology. This photo shows HR 8799 b, c, d, and e, as imaged in infrared light by JWST. The host star’s location is marked with the cartoon star symbol. Credit: NASA, ESA, CSA, STScI, Laurent Pueyo (STScI), William Balmer (JHU), Marshall Perrin (STScI)
Think of a performer on stage. They can’t see the audience through the spotlights aimed at them. To mitigate this, they might block the glare with a hand in front of their face. Astronomers now routinely do this on ground- and space-based telescopes using an instrument called a coronagraph, which creates an artificial eclipse by placing a physical mask in front of the undesirable light source.
But rather than a physical coronagraph, ELF will use a potentially more powerful technique called nulling interferometry. The idea is to combine the beams from its several mirrors so that they interfere and block out the starlight, without a physical mask.
Anyone who has used noise-canceling headphones knows that even if a new shopping center is going up right next door, you will hear nothing. This is because the headphones analyze the incoming sound waves, identify their crests and troughs, and emit a sound that creates destructive interference. Where a crest arrives from outside, the headphones generate a trough; where there is a trough, they generate a crest. The result? A perfectly calm sea of silence.
That principle can be extended to light, which is an electromagnetic wave. ELF will treat the star’s light as “noise” to be cancelled out, keeping only the desired signal — the light from its planets.
A star’s image in a telescope is not a perfect dot, but a slightly blurred spot with a structure that astronomers call the point spread function. The shape, number, and orientation of a telescope’s mirrors and other structures all combine to produce a characteristic diffraction pattern of alternating bright and dark areas in that point spread function. Think of stars in Hubble images, with their sharp X-shaped set of spikes, or the distinctive eight-pointed spikes in JWST photos. These are diffraction patterns. They can be a nuisance — but if your telescope is cleverly designed, they can become a resource.
“We can now create and customize the telescope’s diffraction pattern, so the telescope itself becomes a coronagraph,” Kuhn says. Destructive interference creates a “hole” near the star’s position, allowing the fainter light of the planet to shine through.
ELF is designed so that when its beams are combined, they can form a characteristic pattern of self-interference. “The trick is that, if instead of putting all these mirrors exactly in phase [so all the troughs and peaks of the light waves line up] we shift them a little, adding some relative phase between them, we can control things so that destructive interference is generated at a specific point in the image,” explains Auxiliadora Padrón Brito, a postdoctoral researcher at the Instituto de Astrofísica de Canarias (IAC).
A simulation of ELF’s point spread function — the way an image of a bright star appears when the light from all its mirrors is combined. The mirrors create an image with a lobulated structure that looks almost like a sunflower. Credit:
Kuhn et al., _Light: Advanced Manufacturing_ (2025), DOI 10.37188/lam.2025.033 (CC BY 4.0)
The point spread function when all the mirrors are co-phased, or tilted relative to each other such that a dark region of destructive interference occurs (just below center). By placing the star (and its planets) in this “hole” where the starlight is absent, the planet’s faint light can be directly observed. Credit:
Kuhn et al., _Light: Advanced Manufacturing_ (2025), DOI 10.37188/lam.2025.033 (CC BY 4.0)
## A new type of telescope
Nulling interferometry was first proposed in 1978 as a technique to image exoplanets by Ronald Bracewell, a radio astronomer and engineer at Stanford University. In the 1990s and 2000s, experiments at the Multiple Mirror Telescope and the Large Binocular Telescope in Arizona and Keck Observatory in Hawaii proved the concept. But implementing it on the scale of ELF is a much more complex problem.
To solve it, Kuhn has assembled a team of around 20 scientists and engineers at the Laboratory for Innovation in Opto-Mechanics (LIOM) in San Cristóbal de La Laguna, Tenerife, in the Canary Islands, that includes top-tier experts as well as young talent. Electronics engineer Diego Tamayo Guzmán and neural-networks specialist Natalia Arteaga Marrero are working on a way to control ELF’s mirrors. The 15 primary and 15 secondary mirrors have more than 500 possible degrees of freedom, or independent ways the mirrors can move.
To achieve a coherent image, the primary mirrors must be precisely tuned together “to within tens of nanometers,” says Arteaga Marrero. That’s smaller than the size of a virus. This tuning must happen quickly, on timescales of about 10 milliseconds.
Several team members pose in front of the completed mechanical structure for the SELF telescope after it successfully passed structural testing in early November 2025. From left to right: Nicolas Lodieu, SELF project scientist; Ricardo Diego Garamendi, Added Value Industrial Engineering Solutions (AVS) president; Jeff Kuhn, LIOM project chair; Sergio Salta, AVS Earth Observation Project management; Jose Antonio González Olivera, TEKNIKER Automation and Control Unit researcher; Diego Tamayo Guzmán, control engineer. Credit: LIOM and the Instituto de Astrofísica de Canarias (IAC)
This makes ELF so complex that it cannot be treated like a classical telescope, Kuhn says: It must be controlled via machine learning. Additionally, “we need a different way to manufacture mirrors,” he says, because the system requires mirrors light enough to move with extreme delicacy and speed.
One of the most promising techniques for this is curvature polishing. Rather than grinding down a slab, “we slightly melt the glass on one side” with a laser, Tamayo Guzmán says, to generate a curvature on the other face. This process can yield lighter and thinner mirrors than traditional methods. “The big job is to figure out how much laser power to apply, for how long, and at which locations … [to] achieve the desired curvature.”
Another innovative technique, developed by the French National Centre for Scientific Research (CNRS), is so-called living mirrors, which have a polymer printed on the back. Applying electrical voltage to the polymer changes the mirror’s curvature with more speed and precision than traditional adaptive optics systems that use actuators to deform the mirror. “You can modify it on the fly … depending on what you need at that moment. It’s like a new layer of fine control on top of the 500 degrees of freedom we already have,” Tamayo Guzmán says.
The team is also looking to lighten the telescope structure itself to reduce costs and make the project feasible. One idea comes from a concept developed by American architect Buckminster Fuller in the 1950s known as tensegrity, a combination of the words _tension_ and _integrity_.
Engineers are concerned with two types of stress. Normal stress comes from force that acts perpendicular to a surface. That’s exactly what you want when you hammer a nail into a board, striking along the axis of the nail so the force is perpendicular to the wood. When you miss and the nail bends (and maybe your finger gets smashed), it’s because the blow had a sideways (tangential) component, parallel to the surface. That tangential component produces shear stress, which makes the nail bend instead of sliding in cleanly.
Tensegrity minimizes shear stress by creating structures where the elements carry only normal loads, using precisely tensioned cables that force the pieces to hold each other in place. “We need to create a lightweight structure because we have to build something very large and precise, but affordable. And tensegrity seems one of the best ways to achieve that,” Kuhn says.
Combining precision optics with a network of cables under tension demands a level of calculation and design without precedent. The team is using machine-learning tools to help with the structure’s design. The network of cables and struts must also withstand environmental factors like wind, temperature changes, and seismic vibrations. Sensors and actuators will provide feedback, continuously adjusting tension to maintain the correct destructive interference to block the target star’s light.
Kuhn has assembled a diverse team of experts and up-and-coming researchers to turn SELF and ELF into realities. Pictured here are several members. Back row, from left to right: Víctor Quintero, LIOM project manager; Natalia Arteaga Marrero, postdoctoral researcher; Diego Tamayo Guzmán, control engineer; Auxiliadora Padrón Brito, postdoctoral researcher. Middle row, from left to right: Raquel Conde Viera, LIOM communication manager; Jeff Kuhn, LIOM project chair; Adrián Sánchez Chaves, graduate student. Foreground: Nicolas Lodieu, SELF project scientist. Credit: LIOM and the Instituto de Astrofísica de Canarias (IAC)
Given these extraordinary challenges, the team is starting with a scaled-down version. The Small ELF, or SELF, is already funded by the IAC for construction in late 2026 or early 2027 at the Izaña Observatory on Mount Teide in Tenerife. SELF will comprise fifteen 20-inch (0.5 m) mirrors, fabricated using curvature polishing, with a baseline of 11.5 feet (3.5 m). Although it will initially use a traditional rigid truss structure, SELF is designed so that a tensegrity system can eventually be mounted on it as an upgrade.
Part of SELF’s role is to pave the way for ELF. “SELF could manage to observe a planet up to 10 million times fainter than its central star with the help of the machine-learning system we’re developing,” says Kuhn. One of SELF’s goals is to directly detect the exoplanet Epsilon (ε) Eridani b, about 10.5 light-years away and expected to be near the limits of the telescope’s capabilities. Of course, that planet is a gas giant with no visible surface features. But “with ELF, we hope to observe a planet a billion times less luminous than its star,” says Kuhn.
### SELF: The Small Elf
SELF will be not only a proof of concept of the larger ELF design, but also a valuable science instrument in its own right. It will detect gas giant exoplanets, help astronomers study brown dwarfs and very low-mass stars, and shed light on the dusty disks around young stars from which planets form. Light will bounce off its fifteen 20-inch (0.5 m) primary mirrors, mounted on a ring 11.5 feet (3.5 m) wide, to the secondary mirror, then be combined into a single sharp image. Although SELF will have rigid spokes to hold the rim in place, they can be replaced with tensioned cables later. Credit: _Astronomy_ : Roen Kelly, after LIOM and the Instituto de Astrofísica de Canarias (IAC)
## Mapping other worlds
If ELF succeeds in directly imaging an Earth-like exoplanet — a feat never before accomplished — the planet will not occupy more than a single pixel. But that will enable astronomers to detect surface detail by observing the light that world reflects from its star. Breaking the light up by wavelength into a spectrum reveals the presence of features like oceans, ice, mountains, or deserts. Astronomers will need to watch as the planet rotates, spinning on its axis and moving along its orbit, producing periodic, repeating patterns in its spectrum as features move into and out of view. From those patterns astronomers can infer when certain features are visible and pinpoint their location — working backwards to reconstruct a map of the planet’s surface.
Called cartographic inversion, this technique requires a huge number of consecutive observations to disentangle signals from surface and atmospheric contributions and recover the chemical ingredients present on the planet. “If we have enough data points — a few hundred observations, or even a few thousand — then we can reconstruct a map of the planet, seeing where regions of higher reflectivity, or albedo, are and where regions of lower albedo or reflectivity are,” says Max Dobat, an astrophysics graduate student at the University of Potsdam working on SELF.
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### Recovering features
_Credit: Astronomy: Roen Kelly, after S. V. Berdyugina & J. R. Kuhn, The Astronomical Journal (2019), DOI 10.3847/1538-3881/ab2df3 (CC BY 4.0)_
_To test ELF’s ability to map exoplanet surface features, Kuhn and colleague Svetlana Berdyugina first generated an imagined exoplanet map (top left), then modeled how well the cartographic inversion technique could recover the planet’s features (top right). This planet includes oceans (dark blue), a polar ice cap (light blue), and land covered by plants (green) and desert (yellow and orange). The charts show the amount of reflected light (or albedo), by wavelength, in the two areas outlined in white on each map. The vegetation chart (bottom left) shows an area from the northern hemisphere of the planet covered with vegetation. The rocks chart (bottom right) shows a desert region from the planet’s southern hemisphere. The solid lines show what a perfect spectrum of the “real” exoplanet would look like (the original map). The shaded regions show natural variations in albedo of the rectangular regions observed (i.e., the range of albedos within the boxed areas). The circles depict discrete datapoints from the recovered map, essentially mimicking observations of the planet with ELF — and show that ELF can pick up on differences in reflected light properties between vegetation and rock._
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“[W]e normally see planets simply as a blur,” says Tarter. “The ExoLife Finder has these tricks that it can play … so that when you look at the light that’s reflected by the planet, you can tell whether it’s beachfront, waterfront, or … desert. And that’s getting us there. It won’t show you the best locations to invest in terms of real estate, but it will show you the gross differences of planetary geography.”
Notably, ELF will be able to accumulate data on the same targets night after night. Current methods to obtain spectra from small, temperate planets require us to watch as they pass in front of their star. This only works for planets that happen to be aligned by chance. And “if we are really looking for Earth-like planets” — orbiting at the same distance as Earth around a Sun-like star — “the transit occurs only once a year,” says Dobat. ELF could be a game-changer, dramatically speeding up our ability to characterize exoplanets.
And what about finding life? Kuhn believes we could observe life by capturing the heat it produces, whether by biological or mechanical means. That’s why ELF will also observe at infrared wavelengths of 1.0, 1.2, and 1.5 micrometers, where key molecular features and temperature contrasts between different regions on a planet become easier to detect. “The problem in detecting life is that there is no smoking gun, so to speak,” he says. “It’s a difficult question because we are conditioned by the life we see around us — the only kind we know. But it seems pretty clear to me that life is related to heat.”
Kuhn and fellow University of Hawai‘i scientist Svetlana Berdyugina have published several papers on the kind of thermal signal that large urban and industrial settlements would show on distant planets, an unmistakable sign of an intelligent civilization. For example, “If Los Angeles rotated in our field of view on an exoplanet, it would produce [an] almost-one-percent change in the infrared flux from population alone,” Kuhn says. Transport, industry, power plants, home heating, and commercial buildings would all have a measurable impact as well. “Megacities, solar panels… all of that is detectable.”
This artist’s concept shows the roughly Earth-sized Kepler-452 b (foreground) as a planet much like our own. Although this image is just a guess, ELF could soon let us map planets such as this to determine whether (and where) they have oceans, land, and even vegetation, turning artistic imaginings into reality. Credit: NASA Ames/JPL-Caltech/T. Pyle
## Toward the future
Kuhn hopes that when SELF sees first light around 2027, its proof of concept will attract support from investors and donors to build ELF. Still, it will be at least another decade before ELF might become operational. And given the technical challenges, its success is not a foregone conclusion, other astronomers say.
Mather is impressed by ELF, but notes that any disruptive science effort must deal with many unforeseen problems. “Simulations say it could be good enough,” he says, but he’s still not sure that it will reach the contrast needed to achieve its goals.
In the meantime, NASA has begun developing the Habitable Worlds Observatory (HWO) — the agency’s next flagship observatory after the Nancy Grace Roman Space Telescope. HWO will rely on a traditional large mirror and internal coronagraph to image exoplanets. It is aiming for a launch in the 2040s. But given its cost — which Mather says is “unknown” but “presumably in the JWST category of many billions of dollars” — he is skeptical about NASA’s ability to build it in the foreseeable future.
Another point in ELF’s favor as a ground-based instrument is its size. HWO has to fit inside a rocket fairing for launch, and therefore “is much smaller in aperture than the ExoLife Finder and can’t have nearly the angular resolution,” says Mather.
This also limits how fast HWO can search for exoplanets, notes Ewan Douglas, an astronomer at the University of Arizona who builds exoplanet direct-imaging instruments. “Space observatories are always going to be smaller. … An instrument on the ground would have plenty of photons because now you’re talking about 30-meter-class telescopes rather than 6-meter-class telescopes.”
If ELF can identify Earth-like planets for follow-up, those would be of great value to future observatories with more exotic designs, he adds. For instance, some astronomers have proposed a spacecraft that could fly in formation, tens of thousands of miles away from a telescope like HWO, acting as a starshade to block the light of a host star. This combination would be more powerful than an internal coronagraph. But its ability to search for planets would be limited by the amount of time and fuel it takes to maneuver the starshade into position. “If we know where planets are, it’s much easier to follow them up with space observatories,” says Douglas.
Astrophysicist and science communicator Ethan Siegel believes ELF’s technical challenges are surmountable and comparable to other innovative ground-based telescopes. “The biggest ‘risk,’ ” he argues, “is that we could build it, acquire the spectrum of the many exoplanets-of-interest that we can image, and find nothing dynamical about any of them: just static, barren, cloudless, life-free worlds. But even that implies something profound.”
Kuhn agrees: Whether or not ELF finds life, we will learn something about our place in the universe. A null result “would mean that life is rare, and we should treat it as such.” It might also imply that “life probably did evolve elsewhere too, but then disappeared,” he adds. “All these questions we’re talking about bring the notion of life — and social questions about how life is organized — into a realm where astrophysics actually has something to say about it.”
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_**Thomas Villa** has published astronomy articles in Focus and Coelum magazines. He is based in Santa Cruz de Tenerife, Canary Islands, Spain._
Could this telescope find life on alien worlds? The ExoLife Finder (ELF) looks like no telescope ever built. A spectacular crown of 15 five-meter mirrors perches atop a sprawling metal lattice, res...
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