Hubble spies Neptune's newest dark spot

The Hubble Space Telescope has been busily snapping photos of planets and other objects in the solar system and galaxy for years and some of its latest photos taken last month are of Neptune. In these new photos, taken on May 16, 2016, Hubble has spied a new dark spot in the atmosphere of the cold blue planet. These images aren't the first time that we have seen such a dark spot on Neptune.

The first dark spot scientists were intrigued by on Neptune was seen during the Voyager 2 flyby in 1989. Hubble also snapped images of another similar dark spot in 1994. This latest dark spot is the first one observed in the 21st century. The dark spot is properly a vortex and scientists say that the vortex is actually a high-pressure system and such systems are typically accompanied by bright co-called companion clouds. Those clouds are also visible on the surface of Neptune in the images.

Those bright white clouds form when the flow of ambient air is diverted upwards over the vortex where scientists think the gases freeze into methane ice crystals seen as bright white clouds. "Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains," UC Berkeley astronomer Mike Wong said. "And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth."

The bright clouds were observed in July 2015 by astronomers at the Keck Observatory in Hawaii. At the time, the astronomers believed that the clouds might be bright companion clouds following a dark vortex they were unable to see. Only Hubble has the resolution to be able to observe the dark vortices because these vortices are only seen at blue wavelengths. Scientists help that further study will lead to an understanding of how these dark vortices form and what controls them.