Computer simulations unveil truly alien weather on distant worlds

Washington, Oct 14 : Observations by NASA's Spitzer Space Telescope and the computer simulations used to explain them, hint at weather patterns on distant planets that are truly alien to what are found on Earth.

Approximately 300 planets have been discovered around other stars, and for most of those planets, scientists know little more than the mass and orbital properties of the planet.

However, for a handful of the brightest planets, temperatures have been inferred from observations carried out with spacebased platforms such as NASA's Spitzer Space Telescope.

Those observations, and the computer simulations used to explain them, hint at weather patterns truly alien to our Earth-based experience.

Adam Showman of The University of Arizona led a study explaining how a global atmospheric circulation driven by the dayside heating and nightside cooling can drive weather on the so-called "hot Jupiters", which are Jupiter-like gaseous giant planets that orbit extremely close to their stars.

"These planets are 20 times closer to their star than Earth is to the Sun, and so they are truly blasted by starlight," Showman explained.

Their dayside temperatures reach 2000 or even 3000 degrees Fahrenheit, much hotter than any planet in our Solar System.

Observations conducted last year with the Spitzer Space Telescope showed, however, that for at least one such planet, called HD 189733b, the nightside temperature exceeds 1300 Fahrenheit - much warmer than expected for a wind-free planet.

This shows that winds carry heat from the dayside to the nightside, keeping the nightside warm.

Showman and colleagues performed state-of-the-art 3D computer simulations that, for the first time, coupled the weather motions to a realistic representation for how starlight is absorbed and how heat is lost to space.

The models explain the observed day-night temperature patterns and suggest that, to carry the heat, the planet must have jet streams with speeds reaching a hefty 2 miles per second or 7000 miles per hour.

"According to the observations, the hottest region on the planet is not 'high noon' but eastward of that by maybe 30 degrees of longitude," Showman explained. "Our simulations are the first to explain why that phenomenon occurs," he added.

The planet, HD 189733b, is 63 light years from Earth and is in the constellation of Vulpecula (the Fox).

The star around which the planet orbits, HD 189733, is visible with binoculars from here on the ground, but the planet is much too dim to be detected except with the most powerful space-based telescopes.

ANI