Winds on Neptune travel faster than the speed of sound.
Neptune, the eighth and farthest planet from the sun, has the strongest winds in the solar system. At high altitudes speeds can exceed 1,100 mph. That is 1.5 times faster than the speed of sound. In 1989, NASA's Voyager 2 spacecraft made the first and only close-up observations of Neptune. Detailed images taken by the spacecraft revealed bright, white clouds and two colossal storms whipping around the planet's atmosphere. Neptune is a gas giant composed primarily of hydrogen and helium. Methane gas makes up only one or two percent of the atmosphere but absorbs longer wavelengths of sunlight in the red part of the spectrum, giving the planet its brilliant blue color. Watch the video to see a composite time-lapse assembled from Voyager 2 images of Neptune.