Our Sun’s outer atmosphere, the corona, is millions of degrees hotter than it should be, and no one knows why.

The Oort Cloud, an expanse of icy bodies in the far reaches of our solar system, is shown here in a scene from "Encounters in the Milky Way," a show at New York City's Hayden Planetarium that spawned ...

At the farthest reach of the Sun’s influence, NASA’s Voyager 1 spacecraft has stumbled into a region that behaves less like empty space and more like a furnace, where charged particles heat to tens of ...