A view of the dark vortex in blue light (right) and its bright companion clouds (left). (NASA, ESA, and M.H. Wong and J. Tollefson (UC Berkeley) )

(NASA, ESA, and M.H. Wong and J. Tollefson (UC Berkeley))

NASA just spotted a huge dark spot on Neptune for the first time this century, and it's roughly the size of the United States.

Features of this dark spot, aptly called a dark vortex, were first detected in July 2015, but it wasn't until NASA turned its Hubble Telescope toward the planet in May 2016 that the full extent of the feature was revealed.

A swath of bright 'companion' clouds on the planet's surface are a sign that a 3,000-mile-wide dark vortex lurks beneath.

But what is a dark vortex, exactly?

Despite the doom-inducing name, dark vortices that scoot around Neptune's atmosphere shooting large quantities of gaseous air high up into the atmosphere where it freezes and forms bright 'companion' clouds, according to NASA.

A closer view of the dark vortex and its companion clouds. (NASA)

(NASA)

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

Astronomers previously captured proof of dark vortices on Neptune in 1989 and 1994, but the latest edition is the highest quality yet.The newly released images are all a part of Hubble's Outer Planet Atmospheres Legacy (OPAL) project, aimed at documenting and explaining activity on the most distant planets in our solar system.

Astronomers hope the new higher quality mapping will help them better understand some of the unexplained, like why they exist in irregular shapes and sizes, move at irregular speeds and live for irregular periods of time, according to space.com

Meaning, even though the current dark vortex may be a year old, no one knows how much longer it will last.