Peering at Pluto in preparations for a satellite visit in 2015, the Hubble Space Telescope has spotted a fourth moon orbiting the dwarf planet. The wee moon doesn’t even have a name yet — it’s called P4 for now — and its estimated diameter is between 8 and 21 miles.
That’s right, Hubble spotted something the size of a city from a distance of more than 3 billion miles away.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.