Astronomers have discovered that Uranus is suffering from a bout of wind.

They zoomed in with the Hubble space telescope to reveal a dark spot marking a hurricane two-thirds the size of the United States.

The giant storm, 1,100 miles wide (1,700km) and 1,900 miles long (3,000km), is churning two billion miles away in the atmosphere of the seventh planet from the sun. It is the darkest feature ever seen on the gaseous world and probably formed very recently, say space scientists from the University of Wisconsin-Madison.

They believe the vortex is a sign that spring is coming to the northern hemisphere of Uranus which is strongly tilted over on its axis. Although rare on Uranus, similar spots have previously been observed on its twin planet Neptune.

Heidi Hammel, of the Space Science Institute in Boulder, Colorado, said: “We have hypothesised that Uranus might become more Neptune-like as it approached its equinox. The sudden appearance of this unusual dark feature suggests we might be right.”

Photo: Nasa, Esa