Newfound Mega-Storms on Uranus Pose Planetary Puzzle

Known for calm weather, the seventh planet from the sun is suddenly sporting a series of storms.
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Infrared images of Uranus, made in August at the Keck Observatory, reveal a large storm, brighter than any other feature ever recorded on the planet.


A distant, icy, green giant—the planet Uranus—appears to have unexpectedly awakened from a long slumber. Astronomers have discovered a yet unexplained rash of extreme storms on the normally placid planet.

Peering through the world's most powerful telescopes, the Keck Observatory in Hawaii and the Hubble Space Telescope, a team of researchers based out of the University of California, Berkeley have spotted unusually bright cloud activity in the upper atmosphere of the seventh planet from the sun, which lies about 1.86 billion miles (3 billion kilometers) away.

Over a span of just two days in early August this year, the team spotted eight storms in the planet's northern hemisphere. One of the storms is now considered the brightest ever seen there, accounting for 30 percent of all the reflected light we can see coming off Uranus. (Related: "Auroras Seen on Uranus for First Time.")

Hubble looked at the planet just this past October 24 and found multiple giant storms extending more than 5,592 miles (9,000 kilometers) across, at various altitudes. That is roughly three-quarters of the diameter of Earth.

All these alien tempests appear to be happening above the main methane-laden part of the atmosphere, where the atmospheric pressures are about half of what they are here on Earth.

But one thing is for sure, this busy weather on Uranus has caught scientists completely off-guard.

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This sky chart places Uranus in the constellation Pisces.


Seasonal Shocker

Forecasters predicted a peak in the planet's atmospheric activity during the 2007 Uranian equinox, when the sun shone straight down on its equator. The equinox is an event that happens once every 42 years, twice in the course of the planet's 84-year orbit around the sun.

Astronomers have been watching the weather on Uranus for more than a decade, charting swirling storms near its north pole. Since there is no internal heat source for these storms on the planet, these cloud activities were thought to be driven solely by sunlight.

For that reason, with the northern hemisphere turned away from the sun in recent years, the heating effect was expected to wane. But it hasn't.

Even the amateur astronomy community has sprung into action to document the surprising storms, turning their backyard telescopes on the green giant. Despite using much smaller instruments than their professional counterparts, amateurs were able to observe a different bright spot deeper in the atmosphere of Uranus.

"There definitely is a lot of dynamic activity in Uranus's atmosphere, and we have no idea why," said astronomer and team leader Imke de Pater, of the University of California, Berkeley, at a press conference at a meeting of the American Astronomical Society's Division for Planetary Sciences in Tucson, Arizona, this week.

"Predictions said they should fade away but they didn't, and we hope theorists will now take this mystery on and help explain what exactly is going on."

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A simulated binocular view shows the position of the tiny green disk of Uranus in relation to the star Delta Pisces, faint to the naked eye.


See for Yourself

Backyard sky-watchers can see the giant green world for themselves on any clear night this month.

Uranus is four times as wide as Earth, but since it lies about 1.86 billion miles (3 billion kilometers) away from our planet, it's barely visible to the naked eye at magnitude 5.7-and only in very dark, pristine skies.

However, the planet makes for an easy target with binoculars and small scopes. Look for Uranus lying within the field of faint stars that make up the constellation Pisces, which is now rising above the eastern sky after local nightfall this week.

The faint blue-green disk will appear only 3 degrees to the lower right of the faint naked-eye star Delta Pisces, which shines at 3.5 magnitude. Their apparent separation will be equal to six full moons, making them both fit easily within the field of view of a standard pair of binoculars.

Happy hunting!

Correction: An earlier version of this story incorrectly placed Uranus as the eighth planet from the sun. It is the seventh.

Follow Andrew Fazekas, the Night Sky Guy, on Twitter, Facebook, and his website.

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