In 1989, Voyager 2 made our first close encounter with the stunning blue planet Neptune. Its surprisingly turbulent, storm-laden atmosphere, this far from the sun, was clearly being driven by heat from deep within the planet
The sun, planets and Voyager probes sit inside the tiny yellow dot at right, within a giant sphere called the Oort cloud. This reservoir of trillions of ice chunks extends 100,000 astronomical units out, tethered to the sun by gravity. Astronomers believe these objects got thrown out of the inner solar system as the planets took shape 4.5 billion years ago.