NASA's Spitzer Space Telescope has revealed the first known system of seven Earth-size planets around a single star. Three of these planets are firmly located in the habitable zone, the area around the parent star where a rocky planet is most likely to have liquid water.
A quarter of Earth’s population lacks access to reliable electricity, according to the U.N. Development Programme. More than half of those people have no electricity at all. For many, orbiting solar panels could be a solution.