The Sun is not just a source of heat; it's also the largest lens in the solar system. Its gravity bends light rays like glass, focusing them into a bright ring far beyond Pluto's orbit. If light from a distant planet enters this ring, astronomers could reconstruct its portrait — not a point, but a map with surface details. This is exactly the approach the authors of a new study calculated, modeling the observation of an Earth-like planet around a star 30 parsecs (about 98 light-years) away.
The telescope would need to travel 650 astronomical units from the Sun—16 times farther than Pluto. There, it would see the planet's light stretched into an Einstein ring — a rainbow circle mixing all colors from ultraviolet to infrared. By scanning this ring step by step (128 by 128 points) and splitting the light into 128 shades, you can build a three-dimensional data cube: brightness, color, and time. From that, you can later reconstruct where the planet has oceans, land, and clouds.
The main enemy of such imaging is not distance but the Sun's own corona. It shines millions of times brighter than the target planet. You'd have to accumulate signal seven times longer if you didn't know the exact shape of the lens distortions. The authors showed that if you measure in advance how the Sun's gravity alters the image, you can cut observation time by nearly a factor of three. Then, instead of decades, a few years of work by a single automated telescope would suffice.
This is not a mission verdict but rather an engineering sketch. First, we need to learn to simply obtain images and rough maps. Full spectroscopy of each region will require simultaneous recording of all colors, exquisite calibration, and verification of every processing step. But if we can overcome these challenges, the Sun's gravitational lens will open the way to reading climate maps and searching for biosignatures on planets that today appear only as faint dots.
To reach the focus of the solar gravitational lens at 650 AU, the fastest probe, Voyager 1, would take nearly 300 years: it travels only about 3.6 AU per year.
The idea of using the Sun as a lens to observe exoplanets echoes the plot of Stanislaw Lem's novel 'Solaris', where the planet's ocean itself became a giant optical instrument.