Observing exoplanets directly is extremely challenging. If an alien species 100 light-years from us wanted to see Earth as a single pixel, they’d need a telescope with a primary mirror 90 kilometers (56 miles) in diameter. But there is a way to not just see small exoplanets without needing these impossible telescopes, but actually, map their surface. The secret is to turn the Sun into a giant lens.
Every object with mass warps spacetime, causing light to be bent around it, and this can create the phenomenon known as a gravitational lens, allowing us to see what's behind it. Our Sun, being the biggest object around, can be employed as the lens of a telescope to reach incredible magnifications of distant objects, and that’s how the Solar Gravitational Lens project started.
Such a mission could deliver enough details of an exoplanet surface to see continents and islands (and maybe even cities if they exist) but it comes with many challenges. For the system to work, the Solar lens and the rest of the telescope need to be at 650 times the distance between the Earth and the Sun, or 650 astronomical units (AU).
Voyager 1 is the farthest human-made object from Earth. It has been traveling for 45 years and it is 157 AU from the Sun. The Solar Gravitational Lens needs to send something over four times farther out and in a much shorter time frame. A new paper, available on the preprint server ArXiv, shows that what is needed to make this mission possible is already here or researchers are working on it right now.
“We realized that most of the technologies needed to realize a mission to the SGL either already exist or are in active development," one of the minds behind the project, Dr Slava Turyshev from NASA's Jet Propulsion Laboratory, told IFLScience.
"These include solar sailing propulsion, onboard power, and communication – all of them are now capable to support the mission with even more exciting capabilities to be available soon.”
The team aims to have a spacecraft with a small telescope travel this distance in less than 25 years, which means reaching a higher velocity than any spacecraft we've launched towards the edge of the Solar System. To do that, the team plans to use a solar sail, get the spacecraft close enough to the Sun, and then fly off into the distance at high speed.
This setup means that the target needs to be known in advance as the telescope won’t be able to go and image another object. Also, the spacecraft needs to be light because solar sails require a very large surface area to mass ratio. The team thinks that employing a nanosat that could assemble into a telescope in space would work best.
“One of the most interesting challenges was to scale down some of the systems and instruments to fit within the limits imposed by solar sailing. We need small, capable and inexpensive spacecraft – this is what enables the mission,” Dr Turyshev explained.
“With all that we now need to start developing the flight project – fundraising, community advocacy, team development – this is all exciting and becomes our immediate focus.”
The project is exciting and could have a huge impact on how humans study the other worlds in the Milky Way and in our search for life beyond Earth. Its launch might not be that far in the future if NASA decides to go for it.
“We are ready to fly by 2034. This goal is ambitious, but is feasible,” concluded Dr Turyshev.