INTERSTELLAR TRAVEL AND HOW TO BECOME A SPACE TOURIST

Having explored much of the Solar System, attention is now turning to the stars beyond

- Colin Stuart

As the spacecraft approaches the planet, things seem quite familiar. Sunlight glints off an expanse of blue ocean, and white clouds are corralled by gusts of wind. But a closer inspection is jarring - the continents are in the wrong places. That's because, for all its similarities, this isn't Earth. Instead, we're looking at the first historic images sent back of another world orbiting a star far beyond the Sun. In days gone by, such ideas were little more than a pipe dream. But the tide is turning.

In 2016, the late Stephen Hawking and billionaire Yuri Milner launched their Breakthrough Starshot project to an enthralled press conference. The goal is to one day fire lasers at sails strapped to tiny stampsized spacecraft, launching a swarm of explorers to Alpha Centauri - the nearest star system to Earth. If successful, the journey might only take a few decades. Such interstellar travel is no longer an absurd idea.

As things stand, we only have two distant emissaries of humankind that have departed the planetary system in which we reside: Voyager 1 and 2 - the probes sent to explore the outer planets in 1977. In 2012, measurements of the solar wind suggested Voyager 1 had left the magnetic influence of the Sun - one way of arguing it had departed the Solar System - with its twin reaching the edge in 2018. Yet they are nowhere near the next solar system. That's the problem with space - it really lives up to its name. A trip to the Alpha Centauri system requires us to travel a staggering 4.37 light years. At the speed of Voyager 1 it would take at least 30,000 years to cover that distance.

That's why Hawking and Milner turned to an alternative solution. The goal is to take advantage of advances in technology miniaturisation. "We're already seeing one-tonne spacecraft being scaled down to a one-kilogram CubeSat," says Colin McInnes from the University of Glasgow. "You can imagine a similar device in the future weighing a gram."