100x the power of JWST? Diffractive lenses could alter astronomy forever

The new observatory, currently in the concept phase, would leverage a breakthrough in diffractive lens technology that could drastically cut the cost of developing powerful lenses. 

In an interview with IE, Apai explained that this could allow Nautilus’ instruments to be up to 100 times more sensitive than those of JWST.

Going beyond James Webb’s capabilities

Unlike NASA’s Webb telescope, Nautilus would comprise several units that would fly as part of a network in Earth’s orbit. By using this network, Nautilus could exceed the capabilities of the $10 billion James Webb at a lower cost.

Much like the Event Horizon Telescope, which captured the first direct image of a black hole, a network of units could be used in tandem as a single observatory, allowing for much more powerful observations. 

“As it is currently envisioned, the Nautilus constellation would provide about 80-100 times greater light-collecting power, or sensitivity, than the James Webb Space Telescope,” Apai explained. “It would provide about 1.5 times sharper images. In addition, as it is a constellation of telescopes, it would also allow parallel observations of many different targets.”

“These improved capabilities will be revolutionary,” he continued. “For example, the roughly 100 times greater sensitivity would allow much more efficient and much deeper surveys of the distant (and much younger) universe, a much more sensitive search for Kuiper belt objects and interstellar comets, and it would provide a greatly improved sensitivity for time-domain astronomy – from super-novae to transients, such as gravitational wave counterparts.”

While Webb has vastly improved our understanding of exoplanets with incredibly precise observations, Apai believes Nautilus could go to the next level. Though Nautilus’ improved capabilities will allow for a host of different observations, Apai is most excited by its potential capacity for observing distant alien worlds.

“Most importantly to me,” Apai continued, “[Nautilus] would provide the required sensitivity to probe the atmospheres of about a thousand transiting exo-Earth candidates. This is almost a hundred times larger sample than any other space telescope hopes to achieve.”

To date, NASA has discovered roughly 5,000 exoplanets – the term used to describe planets outside our solar system. 

By studying these planets in greater detail, the scientific community can learn a great deal about the evolution of the cosmos. They may even be able to detect signs of extraterrestrial life in a distant solar system – which is also one of the goals of the James Webb team as well as that of other projects, including ETH Zurich’s LIFE space mission. 

The problem with US space telescopes

The US is the world leader in space observatory development, with NASA leading the James Webb Space Telescope program with its international partners. 

However, the US space industry heavily focuses on large conventional mirror observatories that require increasingly large and complex mirrors. According to Apai and his team, we are reaching the limit of what these observatories can achieve. 

“Around 2015, I became concerned about the trajectory of US space telescopes,” Apai told IE. “I could foresee a large gap between the capabilities our scientific goals would require and what the extension of the current technology could achieve.” 

In fact, part of his team’s process was to envision the capabilities that would be required, given the increasingly ambitious goals of a scientific community searching for extraterrestrial life.

“Given how complex Earth is, and in how many ways other broadly Earth-like planets with alien ecosystems may differ from Earth, I strongly believe that we need to observe a large sample of these worlds to be able to confidently identify and understand those that host life,” Apai said, adding that the required dataset would be hundreds of Earth-like exoplanets. 

“The current paradigm would take another 25-30 years to build” a powerful enough telescope, Apai said. And even then, it “may not significantly exceed the James Webb Space Telescope’s mirror diameter and light-collecting power.” 

In other words, the current approach to research and innovation related to observatories “will not lead to high-fidelity results, even after decades of research and billions of dollars invested.”

Rethinking space observatories

To address the issue, Apai formed a team to explore new experimental technological approaches to developing space observatories. In his words, they set out to “basically re-think space telescopes.”

Ultimately, they devised a concept for a space observatory that would use a low-cost lens in a network. Unlike traditional observatories, like Hubble and James Webb, it will not collect light using mirrors. Instead, it would use a thin lens type known as a diffractive lens. 

Traditional mirrors use refraction to focus light, meaning they change the direction of light as it passes from one medium to another. Diffractive lenses use diffraction, which allows light to bend around obstacles and corners. Scientists achieve this by arranging a pattern of steps and angles on a glass lens.

Traditionally, these types of lenses have been used in small consumer optics, such as virtual reality headsets and camera lenses. They are known for producing blurry images, so they haven’t traditionally been widely utilized in astronomy – other than for internal optics.

“We revisited an exciting idea that was explored two decades ago, but was not feasible with the technology that existed back then,” Apai explained. “Thanks to huge progress in optical free-form fabrication, computer-aided optical design, and our team’s expertise and ideas, the idea of replacing primary mirrors with precision-molded diffractive lenses is now possible.”

Improved diffractive lenses could usher in a new era

Apai’s team at The University of Arizona invented and developed “a greatly improved optical diffractive element” that addresses limitations of past diffractive lens projects and “formed the basis of re-imaging space telescopes,” he said.

Ultimately, their goal is to develop an observatory capable of collecting roughly 100 times more light than James Webb, allowing them to probe the atmospheres of about 1,000 Earth-like exoplanets. This is something Apai stressed is not possible using existing technologies.

According to Apai, “we are at the perfect moment in history to re-think how we build space telescopes: The cost of getting to space has dropped rapidly due to reusable launch vehicles – a new era ushered in mostly by SpaceX.”

“Given that the cost of launching space telescopes is no longer the barrier as it used to be, and that much progress has been made in automated, high-precision manufacturing, we can change the current paradigm,” he explained. “Rather than building a single unit – essentially a prototype – like Hubble or James Webb, we want to create a constellation of identical unit telescopes. By replicating the telescope optics and the spacecraft, we aim to benefit from the economy of scale.”

Apai’s team has also demonstrated that their diffractive lens can be mass-produced – an essential factor given that they would require many lenses for an entire network of several units.

“With appropriate funding, we estimate that it would take about 8 to 10 years to build the first unit telescope, which would already be larger and more sensitive than JWST, though simpler in design,” Apai told IE. “After that, with efficient replication, the constellation could be built up in another 5-10 years. This would be a somewhat shorter time than the time between the launches of NASA flagship missions such as Hubble, JWST, and the upcoming Habitable Worlds Observatory, but the increase in sensitivity would be substantially greater than between previous flagship observatories.”

If future tests go according to plan, Apai’s team will have unlocked a new paradigm for space observatories. In the process, they will have also developed a network capable of outperforming the world’s best space observatories by some distance.