Plans to explore the nearest star system rely on light sails — reflective panels that are propelled by light. These craft travel so fast that they will have little time to explore their destination, but altering the way the sails are used could help.

An Earth-sized planet orbits Proxima Centauri, the Sun's nearest neighbour, which is 1.3 parsecs (4.2 light years) from Earth. Astronomers hope to send a fleet of miniature probes to explore it and the neighbouring twinned stars of Alpha Centauri. Under current proposals, these laser-propelled craft would take 20 years to reach the stars and zip past them in just a few hours (see Nature 542, 20–22; 2017). But René Heller of the Max Planck Institute for Solar System Research in Göttingen, Germany, and Michael Hippke of Neukirchen-Vluyn, Germany, say starlight could be used to slow down a sail-carrying probe, allowing more data about the planet to be collected.

In their proposal, the sail would shift direction as it passed Alpha Centauri so that starlight and the stars' gravitational pull could slow it down. The probe would then swing into orbit around Proxima Centauri, allowing multiple fly-bys of Proxima's planet. Using this set-up, a probe would take roughly a century to get from Earth to Alpha Centauri, and another half-century to reach Proxima.

Astrophys. J. 835, L32 (2017)