The icy, blue planets at the edge of our solar system are offering up their stormy secrets as they go through extended summer seasons.
NASA’s Hubble Telescope nabbed new images of the two giant planets in September and November 2018. The snaps show both planets bathed in their vivid blue hues, caused by atmospheric methane, but also highlight huge storms dominating the planet’s northern hemispheres.
On Neptune, a 6,800-mile (around 11,000-kilometre) wide storm is visible. The dark patch rests next to a number of bright white “companion clouds”, as NASA calls them. The “mysterious dark vortex” has been snapped a number of times in the past. When Voyager 2 zipped past in 1989 it noticed two storms and Hubble has been watching the planet since launch in 1990. Since 1993, it’s spotted three other storms brewing over Neptune.
Scientists aren’t sure what causes the dark vortices to form on the solar system’s fourth-biggest planet. However, NASA notes that in 2016 there were more clouds in the region than is usually observed right before the vortex appeared. The vortices may arise from deeper within Neptune — which is mostly composed of hydrogen and helium — and then become visible to Hubble (and us!) when they rise to high enough altitudes.