Astronomers have spotted a “dark vortex” swirling in Neptune’s atmosphere.
Using high resolution images captured in May by the Hubble Space Telescope, researchers say the vortex is about the size of the continental United States.
The vortex is a high pressure system and is accompanied by bright clouds. In 2015, astronomers spotted clouds and later a dark spot nearby. The May 2016 images confirmed the presence of the vortex.
"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."
Vortices on Neptune have been spotted before. In 1989, the Voyager 2 spacecraft saw one, and in 1994, Hubble pinpointed one.
Astronomers say the vortices “have exhibited surprising diversity over the years, in terms of size, shape, and stability (they meander in latitude, and sometimes speed up or slow down).”
They also have relatively short lifespans compared to anticyclones seen on Jupiter, which “evolve over decades.
Further study should yield a better understanding about how vortices develop, what causes them to move and how they interact with the environment, researchers said.
Neptune is roughly 4.3 billion kilometers from the Sun, and it takes 165 Earth years to make one orbit of the sun.