New dark feature spotted on Neptune

A new dark spot on Neptune was captured by the Hubble Space Telescope. Hubble/NASA

For the first time since 1994, the Hubble Space Telescope has spotted a dark vortex on Neptune.

The vortex is an area of high pressure on the planet. As this high pressure forms, it creates brighter companion clouds comprised of methane ice crystals.

READ MORE: New Hubble map of Jupiter reveals new features of raging storm

“Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains,” said University of California at Berkeley research astronomer Mike Wong. “And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth.”

The full visible-light image at left shows that the dark feature on Neptune lies near and below a patch of bright clouds in the planet’s southern hemisphere. The full-colour image at top right is a close-up of the complex feature. UC Berkeley

In July 2015 amateur astronomers using powerful telescopes reported spotting bright features on Neptune. It was theorized that the clouds were a result of a dark vortex that was invisible. These vortices are only visible at blue wavelengths and only Hubble has a high enough resolution to spot them.

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In September, a long-term Hubble project that takes yearly images of planets photographed the dark vortex. It was spotted a second time, indicating that this is a long-lived feature on the planet.

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The vortex was officially reported on May 17, 2016 and further investigated by a team at the University of California Berkeley.

Storms in the cloud tops of planets are fairly commonplace: Jupiter’s Great Red Spot, which has lasted hundreds of years, is a perfect example. Smaller vortices on the planet come and go as well. And these storms have also been spotted on Saturn.

Neptune’s vortices exhibit a lot of variability and astronomers hope to better understand why they can vary in size, shape and why they sometimes cross latitudes and change speed.