The Alpha Centauri star system is a fair old hike. At 25 trillion miles (4.37 light years) away, it would take around 30,000 years for us to roll into the area, and that's if we hitched a ride on today's fastest spacecraft. If the latest idea from the cosmically inquisitive Stephen Hawking comes to fruition, however, we could reach this neighboring stellar system within 20 years of launch.

The US$100 million Breakthrough Starshot program, which also has the backing of entrepreneur Yuri Milner and Facebook CEO Mark Zuckerberg, will investigate how small, lightweight spacecraft could be used to cut the travel time between us and our nearest star system. This could see these "nanocraft" zipping along at 20 percent of light speed, or more than 1,000 times faster than the spacecraft we use today.

These nanocraft would be based on gram-scale chips carrying cameras, photon thrusters, power supplies, navigation and communication equipment, offering the same functionality as a conventional space probe. These chips would be combined with LightSails no more than a few hundred atoms thick to pull the nanocraft along at up to 100 million mph, propelled by huge laser arrays.

Astronomers guess that there's a reasonable chance of finding an Earth-like planet sitting in the habitable zones within the Alpha Centauri system. Once the nanocraft arrive, they would gather scientific data and transmit it back to Earth, where it would be received through the same laser array used for launch over four years later.

All of this would require some serious legwork here on the ground, including construction of a kilometer-scale laser array beamer, capacity to store a few gigawatt hours of energy for each launch and the ability to launch a mothership loaded with thousands of nanocraft into high altitude orbit.

Beyond that, the proposal anticipates certain advances in technology, but it is claimed that the main elements of the proposed system are based on those already available, or those "likely to be attainable in the near future." The program will kick off with a research and engineering phase, which is expected to take a number of years.

The Breakthrough Starshot proposal is part of a wider program launched by Hawking and co last year called the Breakthrough Initiatives, aimed at galvanizing the search for extraterrestrial life. Among the other endeavors already launched under the banner is a 10-year mission to scour the closest 1,000,000 stars on the galactic plane for signs of intelligent life and a million dollar competition to inspire ideas for how we could communicate with such life should it be found.

"Earth is a wonderful place, but it might not last forever," says Stephen Hawking, "Sooner or later, we must look to the stars. Breakthrough Starshot is a very exciting first step on that journey."