By utilizing a phenomenon known as gravitational lensing, we can use the Sun as a gigantic telescope to look deep into space.
Close-Up of Solar Flares Erupting from the Sun
Some incredibly powerful telescopes have provided us with stunning views of the universe, allowing us to look back to the early days of cosmic history. Observatories like the James Webb Space Telescope (JWST) represent remarkable technology, costing billions of dollars and taking decades of work to develop.
But what if we could access an even better telescope? This would not be a conventional telescope. It wouldn’t even come with a lens. Yet, it would be the most powerful telescope we have ever created. This telescope would use the Sun itself.
A photo of the Sun taken on August 29, 2024. (Photo: Mark Johnston).
Consider the JWST. With a mirror diameter of 6.5 meters, the JWST can achieve a resolution of about one-tenth of an arcsecond, which is approximately 600 times better than the human eye. At that resolution, this telescope can see details on a coin placed 40 kilometers away or capture the image of a football located 550 kilometers away.
Another example is the Event Horizon Telescope, which is essentially a network of individual devices scattered around the globe. By carefully coordinating its components, this telescope has provided us with impressive images of the gas disks surrounding supermassive black holes. To achieve this, it reached an impressive resolution of 20 microarcseconds. At that resolution, the telescope could detect an orange on the surface of the Moon.
A larger telescope would require gigantic disks or a network of antennas flying through the solar system, both demanding significant leaps in our technological capabilities.
Solar Telescope?
While the Sun may not resemble a conventional lens or mirror, it has a massive amount of mass. According to Einstein’s theory of general relativity, massive objects warp the spacetime around them. Any light passing near the surface of the Sun is deflected, and instead of continuing in a straight line, it converges towards a focal point, along with all other light passing by the Sun at the same time.
Astronomers have used this effect, known as gravitational lensing, to study the most distant galaxies in the universe. When light from these galaxies passes near a massive galaxy cluster, the mass of that cluster amplifies and magnifies the background image, allowing us to see much farther than normal.
“Solar Gravitational Lens” offers an almost unbelievable high resolution. It’s like having a telescope mirror as wide as the entire Sun. A device placed at the precise focal point could harness the gravitational bending of light by the Sun to allow us to observe the distant universe with an astonishing resolution of 10^-10 arcseconds—about a million times more powerful than the Event Horizon Telescope.
Of course, there are challenges in using the Sun’s gravitational lens as a natural telescope. The focal point of all this light bending is located over 542 times the distance from the Earth to the Sun. This distance is eleven times that to Pluto and three times the distance reached by humanity’s farthest spacecraft, Voyager 1, launched in 1977.
So, we not only have to send a spacecraft farther than ever before, but we also need enough fuel to remain there and maneuver around. The images produced by the solar gravitational lens would span tens of kilometers of space.
Plans to utilize the solar lens have existed since the 1970s. Most recently, astronomers have proposed developing a fleet of small, lightweight cube satellites that would deploy solar sails to accelerate them to 542 astronomical units (AU). Once there, they would slow down and coordinate their operations, generating images and sending data back to Earth for processing.
While it may seem odd, this concept is not too far from reality. And what would we gain from such a super telescope? For example, if it were pointed at Proxima b, the closest known exoplanet, it would provide a resolution of 1 kilometer. The JWST hopes to achieve the capability of imaging exoplanets, where the entire planet fits within a few pixels; the solar gravitational lens puts those ideas into perspective…
The solar telescope would surpass any telescope we could build in the next few hundred years.
