As an ice giant, Uranus is about four times bigger than the Earth's diameter. It has an atmosphere made up of mostly helium and hydrogen, tinged with just enough methane to give the planet a blue glow.
Because it's so far away, situated 19 times farther from the Sun than the Earth is, astronomers only see details on its surface through W. M. Keck Observatory telescopes. It is through these very same telescopes that a team, which was led by Imke de Pater, professor at the University of California, Berkeley, saw the storms swirling in Uranus.
The planet undergoes equinox every 42 years, with the most recent being in 2007. During this time, storms can be expected on the planet so astronomers are baffled that the planet is exhibiting rocky weather after an equinox.
De Pater's team detected eight big storms on Uranus' northern hemisphere from Aug 5 to 6. One of the brightest of the stroms was at 2.2 microns, the wavelength that allows for cloud sensing at levels beneath the tropopause or just 50 percent of the pressure of the Earth's surface. With the size of the storm, it accounted for about 30 percent of all reflected light coming from Uranus at that wavelength.
Amateur astronomers also caught on to the unique event and were able to see for themselves the storms on Uranus' surface.
Marc Delcroix was one of them, successfully capturing Uranus' storms in photographs using a Pic du Midi one-meter telescope.
"I was so happy to confirm myself these first amateur images on this bright storm on Uranus, feeling I was living a very special moment for planetary amateur astronomy," he said.
While this event was also part of the bad weather in Uranus, the storm spotted by amateur astronomers was not the same one de Pater's team noticed. Delcroix's was just at 1.6 microns while the biggest storm detected by the Keck Observatory was, again, at 2.2 microns.
According to planetary scientist Larry Sromovsky from the University of Wisconsin, the color and form of storm clouds hint that the storm is connected to a vortex deep within Uranus' atmosphere, much like two large complexes of clouds usually observed during an equinox.
De Pater and Sromovsky, along with Pat Fry from the University of Wisconsin and Heidi Hammel from the Association of Universities for Research in Astronomy, reported their observations at the American Astronomical Society's Division of Planetary Sciences meeting in Arizona.
