The baffling 'Y clouds" of Venus invisible to the naked eye but seemingly at odds with planetary dynamics has finally received a convincing explanation over a half century after they were first discovered.

The Y clouds, which are visible only in the ultraviolet spectrum, practically cover the entire planet. This dark anomaly in the Venusian atmosphere is shaped like a Y with a stem resting along the planet's equator.

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This huge structure's arms are over 17,000 kilometers long while the stem about 19,200 km long.

Scientists previously thought it was simply a group of clouds but data later revealed the structure moved like a single entity and also traveled at a different speed than its environment, both of which were puzzling as they seemed to defy natural laws.

Scientists have long thought the Y clouds were caused by waves in the atmosphere of Venus. It has been long known that interacting waves can theoretically generate strange geometric features in planets. One of these oddities is the giant hexagon circling Saturn's north pole.

Astronomers from the Institute of Astrophysics of Andalusia (Instituto de Astrofísica de Andalucía, IAA-CSIC) in collaboration with the University of the Basque Country and the Institute of Astrophysics and Space Sciences of Portugal, have finally described the mechanism that sustains the structure of the Y clouds.

They have also, for the first time, succeeded in reproducing its evolution in the course of one month.

"The conclusion was that it could only be a wave or a periodic alteration of atmospheric variables, but we didn't know which one," said Javier Peralta, IAA-CSIC researcher in charge of this study.

He said these dark structures in the Y cloud revealed the massive presence of a still unknown compound that absorbs ultraviolet radiation and obscures the region where they are concentrated.

Peralta and his colleagues found that centrifugal forces might have created the Y feature. Centrifugal force flings items on a rotating body away from the center of rotation.

They found this new wave can make the unknown ultraviolet-light-absorbing material on Venus expand upward. This explains the dark color of the Y feature. This new wave can also explain the bizarre shape of this dark structure.

Astronomers received an added bonus from tracking these structures. They discovered the odd "super-rotating" nature of Venus' atmosphere.

Venus takes 243 days to rotate around its axis, the slowest rotating body in the solar system. On the other hand, Venus' atmosphere spins around the planet in only four days, the fastest rate in the solar system.

"A wave with the size of the Y must play a key role in explaining why the atmosphere rotates sixty times faster than the surface, so it was crucial to understand it," said Peralta.

These findings could shed light on the way other slowly rotating planets behave.

"We expect that the number of slowly rotating exoplanets will shortly increase, and we already provided a list of up to 20 plausible candidates previously," Peralta said.