A novel 'gravity telescope' concept could help us explore life on exoplanets
There is much discussion about the James Webb Telescope, but what if we told you there was a new device that could capture alien worlds floating beyond our solar system with incredible clarity? On Tuesday, a team of Stanford researchers revealed a futuristic telescope concept in The Astrophysical Journal that may just revolutionize how we explore space beyond our solar system.
Using the Sun to examine faraway worlds
It's called the “gravity telescope,” and it would use the Sun to examine faraway worlds previously unreachable to Earth's astronomers.
“We want to take pictures of planets that are orbiting other stars that are as good as the pictures we can make of planets in our own solar system,” said in a statement Bruce Macintosh, a physics professor at the School of Humanities and Sciences at Stanford and deputy director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).
“With this technology, we hope to take a picture of a planet 100 light-years away that has the same impact as Apollo 8’s picture of Earth.”
How would the new telescope capture such images? Through a process called gravitational lensing that was first observed in 1919 during a solar eclipse. At the time, the moon obstructed the light from the sun, allowing scientists to see stars near the sun offset from their known positions.
However, it wasn't until 1979 that Von Eshleman, a Stanford professor, revealed a process by which astronomers could exploit the solar gravitational lens. In 2020, the imaging technique was further developed to observe planets by Slava Turyshev of California Institute of Technology’s Jet Propulsion Laboratory.
A new and vastly improved method
Today, Alexander Madurowicz, a Ph.D. student at KIPAC, was inspired by Turyshev's work to engineer a new method that can reconstruct a planet’s surface from a single image taken looking directly at the sun.
“By unbending the light bent by the sun, an image can be created far beyond that of an ordinary telescope,” Madurowicz said. “So, the scientific potential is an untapped mystery because it’s opening this new observing capability that doesn’t yet exist.”
Now, if the team of researchers can get together the funding and technology to further develop this technique, it will open a world of imaging possibilities for distant until recently impossible-to-view planets and for the process of evaluating life on other planets.
“This is one of the last steps in discovering whether there’s life on other planets,” Macintosh concluded. “By taking a picture of another planet, you could look at it and possibly see green swatches that are forests and blue blotches that are oceans – with that, it would be hard to argue that it doesn’t have life.”
The prospect of combining integral field spectroscopy with the solar gravitational lens (SGL) to spectrally and spatially resolve the surfaces and atmospheres of extrasolar planets is investigated. The properties of hyperbolic orbits visiting the focal region of the SGL are calculated analytically, demonstrating trade-offs between departure velocity and time of arrival, as well as gravity assist maneuvers and heliocentric angular velocity. Numerical integration of the solar barycentric motion demonstrates that navigational acceleration is needed to obtain and maintain alignment. Obtaining target ephemerides of sufficient precision is an open problem. The optical properties of an oblate gravitational lens are reviewed, including calculations of the magnification and the point-spread function that forms inside a telescope. Image formation for extended, incoherent sources is discussed when the projected image is smaller than, approximately equal to, and larger than the critical caustic. Sources of contamination that limit observational signal-to-noise ratio (S/N) are considered in detail, including the Sun, the solar corona, the host star, and potential background objects. A noise mitigation strategy of spectrally and spatially separating the light using integral field spectroscopy is emphasized. A pseudo-inverse-based image reconstruction scheme demonstrates that direct reconstruction of an Earth-like source from single measurements of the Einstein ring is possible when the critical caustic and observed S/N are sufficiently large. In this arrangement, a mission would not require multiple telescopes or navigational symmetry breaking, enabling continuous monitoring of the atmospheric composition and dynamics on other planets.