Renowned cosmologist Stephen Hawking and other distinguished researchers joined internet investor and science philanthropist Yuri Milner at One World Observatory to announce a new Breakthrough Initiatives project focused on space exploration and the search for life in the Universe.

Called Starshot, the $100 million research and engineering program aims to demonstrate proof of concept for light-propelled nanocrafts. Such starships could fly at 20 percent of light speed and capture images of possible planets and other scientific data in our nearest star system, Alpha Centauri, just over 20 years after launch. The program will be led by Pete Worden, the former director of NASA Ames Research Center, and advised by a committee of world-class scientists and engineers.

“The human story is one of great leaps,” says Milner, founder of the Breakthrough Initiatives. “Fifty-five years ago today, Yuri Gagarin became the first human in space. Today, we are preparing for the next great leap—to the stars.”

The Alpha Centauri star system is 25 trillion miles (4.37 light years) away. With today’s fastest spacecraft, it would take about 30,000 years to get there. Breakthrough Starshot aims to establish whether a gram-scale nanocraft, on a sail pushed by a light beam, can fly over a thousand times faster.

Starshot brings a Silicon Valley approach to space travel, according to Milner, capitalizing on exponential advances in certain areas of technology since the beginning of the 21st century. The vessel, for example, will house StarChip, a fully functional space probe the size of a gram-scale wafer. It’s designed to carry cameras, photon thrusters, power supply and navigation and communication equipment.

Advances in nanotechnology are also producing increasingly thin and light-weight metamaterials, promising to enable the fabrication of Starshot’s lightsails, meter-scale sails no more than a few hundred atoms thick and at gram-scale mass.

Milner expects the StarChip can be mass-produced at the cost of an iPhone and be sent on missions in large numbers to provide redundancy and coverage. Its light beamer, a phased array of lasers used to propel the vessel through space, is modular and scalable. Once it is assembled and the technology matures, the cost of each launch is expected to fall to a few hundred thousand dollars.

The research and engineering phase is expected to last a number of years followed by development of the ultimate mission to Alpha Centauri. That mission would require a budget comparable to the largest current scientific experiments and would involve several smaller projects, including building a ground-based kilometer-scale light beamer at high altitude, launching a mothership to carry thousands of nanocrafts to a high orbit and generating and storing a few gigawatt hours of energy per launch.

“We take inspiration from Vostok, Voyager, Apollo and the other great missions,” said Worden. “It’s time to open the era of interstellar flight, but we need to keep our feet on the ground to achieve this.”