A Silicon Valley billionaire wants to visit the nearest star. So armed with a pile of cash and a little help from his friends—including physicist Stephen Hawking—entrepreneur Yuri Milner developed a project called Breakthrough Starshot, which was unveiled yesterday. Got questions about this imaginative new venture? Here’s everything you need to know.

The goal is to send spacecraft the size of postage stamps to Alpha Centauri, the nearest star system to Earth. Each nanocraft, or StarChip, will be packed with cameras, thrusters, and navigation and communications equipment—the kinds of things Silicon Valley is good at making tiny and sticking on chips. Once in space, the craft will be propelled by light rather than combustion, courtesy of a thin, perhaps