Breakthrough Starshot, announced 12 April 2016, is a US$100 million program by Breakthrough Initiatives to develop a proof-of-concept light sail spacecraft fleet capable of making the journey to Alpha Centauri at 20% the speed of light (60 million m/s or 215 million km/h) taking about 20 years to get there, and about 4 years to notify Earth of a successful arrival.
Mark Zuckerberg shared on Facebook : "I'm proud to join Yuri Milner and Stephen Hawking for a new space initiative to go beyond our nearby planets to explore other stars for the first time in human history.
Our nearest star, Alpha Centauri, is 4.3 light years or about 25 trillion miles away. Even with today's fastest spacecraft, it would take 30,000 years to get there. That's too long.
The new idea here is that instead of using large spacecraft burning fuel like people have in all traditional space travel, we're going to create a fleet of tiny spacecraft -- or nanocraft -- that we can accelerate to 20% of the speed of light using an array of laser beams from our planet's surface. At that speed of 100 million miles per hour, it will only take 20 years to reach Alpha Centauri. This is a completely new way to think about space travel and exploration.
The reason this project is important is recent research has found many stars have planets within a distance where they could have water to sustain life. That is, they're close enough to their star that any water isn't frozen but not so close that it has all evaporated. But just because a planet is in this habitable zone doesn't mean it has water and is a place we can actually live. For example, Mars has no water, so it would be difficult to ever live there. It's quite possible the closest planet that humans could actually live on is orbiting Alpha Centauri, and the only way to know that for sure is to visit close enough to photograph the planet, which is what this project will do.
Over the years, Yuri and I have worked on a number of science initiatives together, including creating the Breakthrough Prize. I'm excited to support this latest initiative with Stephen Hawking, and to help bring human space exploration to the stars."
If an Earth-size planet is orbiting Alpha Centauri, Breakthrough Starshot will try to aim its crafts within 1 Astronomical Unit (150 million kilometers or 93 million miles) of it. From this distance, its four cameras could potentially capture an image of high enough quality to resolve surface features.