A futuristic telescope Design could one day allow scientists to finally look at fine details of the atmospheres of Earth-sized exoplanets – and confirm whether some are potentially habitable worlds. To do this, it would use the sun’s gravity and a quirk of Einsteinian physics.
The so-called “gravity telescope” would use the Sun to study very distant worlds, perhaps in a few decades if funding, technology and engineering get right together, new research shows.
Co-author and exoplanet researcher Bruce Macintosh of Stanford University narrates The opposite the work of his team, published on May 2 in The Astrophysical Journalbuilds on decades of research by engineers and scientists striving to learn more about the 5,000 known planets outside our solar system.
How does it work? — The concept of using the Sun as a telescope is also decades old, but articles like this newly published work can glean more details about the initiative, he says.
The Gravity Telescope uses a long-established astronomical technique called gravitational lensing. The effect occurs when a massive object in the foreground (like a galaxy) bends the light of a distant object in the background (like a planet). Einstein correctly predicted this effect at least as early as 1936.
The paper envisions using a Hubble-class telescope at long range (550 astronomical units, or Sun-Earth distances). That’s relatively close astronomically, but still scary. “It’s about two times farther away than Pluto, or about seven or eight times farther away than the Voyager spacecraft,” says Macintosh.
The 550 AU distance is the focal range of the Sun’s gravitational lens, which allows the source that requires magnification (the exoplanet) and the Sun’s lens to be aligned so that the telescope can see distant objects behind it, which are caused by the gravity of the planet sun to be broken.
To go into detail – Macintosh warned that his team weren’t engineers, but the telescope would likely need to be fitted with a sunshade (a coronagraph) to shield it from stray light and block the Sun’s light. Coronagraphs are well proven in space and are fitted to some instruments onboard the James Webb Space Telescope.
Gravitational lensing events of individual stars or planets are usually random. Astronomers usually don’t know the background objects even exist until they appear in an archival image from a telescope that happens to be looking in that area of the sky. However, NASA’s James Webb Space Telescope plans to deliberately use the technique for a recently discovered old star that will be moving behind foreground members of a star cluster.
In theory, it sounds like it would be even easier to use the sun as a gravitational lens. After all, it’s closer to us, so gravitational lensing would be much more robust. Also, the Sun would be used to study planets already discovered, making the study process more efficient. However, there are significant technological questions that astronomers and engineers must address before this vision can become a reality, Macintosh said.
“Part of the point of this work was to really look closely at the math and physics and understand how well it would work to have a picture that you could make [of a planet]and how you would take that picture,” says Macintosh, who is also associate director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).
In theory, the futuristic telescope could be able to look at the spectrum of a distant rocky planet’s atmosphere to look at the signals from chlorophyll, try to see the “shiny and reflective” signal from water, or the chemical composition of clouds investigate. he added.
By comparison, NASA’s newly launched James Webb Space Telescope will study the atmospheres of gas giants in less detail. According to Macintosh, in 20 years, astronomers will commission observatories to study the signature of oxygen in rocky world atmospheres.
The gravitational telescope would therefore be the next logical step and a significant milestone. “I think there’s also something fascinating about getting this first picture of a life-bearing world,” he said.
Echoing the pioneering 16th-century telescopic studies of the Moon, Saturn’s rings and Jupiter with one of the first telescopes, he added: “It’s like Galileo looking through the telescope for the first time.”
“One of the things about the sun as a lens is that it’s actually not a very good lens,” Macintosh joked. “If someone tried to sell you this lens, we would send it back to the store.”
The disadvantages – A major hurdle is the sheer brightness of the Sun, which if handled improperly, would easily wash out an exoplanet’s subtle light. The lens can also be subject to spherical aberration and astigmatism, according to a 2021 study in Physical Check D discussed.
However, feasibility studies on solar lenses have been conducted for decades, including a key 1979 study by Stanford Professor Von Russel Eshleman, now Professor Emeritus of Electrical Engineering. Eshelman considered how both astronomers and spacecraft could use the lens, and his article helped with the latest study.
The Voyager spacecraft, successful as it was, provides an excellent case study of how technology may need to change to make this futuristic telescope more efficient. Their signals take almost a day to reach Earth via radio, or more precisely 21.5 hours for Voyager 1 and about 18 for Voyager 2. That’s also how long it takes for a NASA signal to travel through Earth’s Deep Space Network radio dishes send a command to the distant spacecraft.
It was the best we could get with 1970s technology, but Macintosh said the new telescope would ideally use artificial intelligence and data advances in compression technology to speed communication back and forth, possibly using lasers, according to numerous recent NASA feasibility studies with spacecraft. (This would speed up the data transfer rate, although lasers, like radio waves, are limited by the speed of light.)
“The telescope would need to be fairly autonomous, both to plan the observations and to track the planet,” he said. “It would also need to make intelligent decisions about what data to send back and how to compress it.”
All of this assumes, of course, that the telescope could reach this region at all. Considering that Voyagers was launched 45 years ago and entered interstellar space only within the last decade, the new study calls for more advances in rocket technology to bring the Hubble-sized exoplanet lens telescope to market faster bring.
But once the telescope is in place, lead author Alexander Madurowicz, a Ph.D. student at KIPAC, wrote that the telescope would be a “remarkable” milestone in astronomical imaging.
“Recently, the Event Horizon Telescope (EHT) collaboration released their famous image of the supermassive black hole at the center of galaxy M87,” he said in a blog post. “By using a huge interferometric array of radio dishes spread across the Earth’s surface and combining all the measurements to appear like a single Earth-sized telescope, they were able to produce the highest angular resolution image ever.”
The solar gravitational lens, he said, would produce images with an angular resolution of 25 nanoarcseconds, which would be much finer than the EHT’s 25 microarcsecond resolution. In other words, the solar lens would be a major milestone in detail imaging.
What’s next – Madurowicz also provided a path for future engineers to tackle some of the larger challenges of the future. “First, a target planet must be identified and located in the sky with sufficient accuracy,” he says. “Then the telescope must navigate to align the orbits of the spacecraft, the Sun, and the target planet.”
“Eventually, optical instrumentation strategies that can remove contaminating light from the Sun, the corona, the host star and background objects must be employed to improve the signal-to-noise ratio,” he adds.