Scientists devise tiny spacecraft with giant light sails to visit nearest exoplanet

Astronomers announced several months ago that there is most likely a small Earth-like planet in orbit of Proxima Centauri. That’s a big deal because Proxima Centauri happens to be the closest star to Earth, at just a bit over four light years away. That’s still an insurmountable distance for human exploration. But it’s possible a probe could make it to the Centauri system in the not-too-distant future. Scientists are already working on theoretical ways we could send a tiny probe to investigate Proxima Centauri with the aid of a giant laser.

The exoplanet in question is known as Proxima b. It’s in orbit of Proxima Centauri, one of three stars in the Proxima system. It’s the smallest of the three, a red dwarf that’s dimmer and cooler than the sun. The planet orbits very close to Proxima Centauri (it completes an orbit every 11.2 Earth days), meaning it’s in the habitable zone of that cooler star. Analysis points to a planet that’s around 1.3 times the mass of Earth. That means it’s probably a rocky planet with the potential for liquid water and maybe even life.

On the scale of the universe, 4.2 light years is nothing, but it’s a long way for us. Sending anything large enough to carry humans to Proxima Centauri is impossible right now — it would take roughly 50,000 years with current technology. But a small craft with solar sails might be able to make it in a few decades. Astrophysicists Michael Hippke and René Heller have published a study that presents a possible way to reach Proxima Centauri and look for Proxima b.

The ambitious plan is based on the Breakthrough Starshot initiative, a scheme to launch an unmanned spacecraft past nearby stars with solar sails. It calls for a large laser in space near Earth that could beam solar energy at the sails, accelerating it to a high speed. However, this craft would only have a few moments to snap photos of the target before it was out of range — it would be a flyby like New Horizons and Pluto, but a lot faster.

This artist’s impression shows the planet Proxima b orbiting in the Goldilocks zone around the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Image: ESO

The revamped Proxima b version still needs a laser system for propulsion, but the spacecraft itself would be about the size of a bar of soap. The sails would have an area of roughly 1 million square feet, the same as 14 soccer fields. With so little mass to move, the craft could reach 20% the speed of light. What’s different here is that the sail would be reoriented to slow the probe down as it approached the Centauri system. It would enter orbit of one of the larger stars, then use a series of maneuvers to hop over the Proxima Centauri system where Proxima b is located.

The trip would take around 20 years, but there are a lot of missing pieces of the puzzle before we could even think about launching. How we would keep a large solar sail intact at 20% the speed of light is one unknown. The laser system that would beam energy to the sail is still entirely hypothetical as well.