Winds on hot Jupiter exoplanet blow the wrong way

Enigmatic planet also has inflated size and strange spectrum of surface light emissions.
By Laurel Kornfeld | Jan 24, 2018
Scientists have discovered a hot Jupiter, or gas giant planet in a close orbit around its star, with a wind that blows in the opposite direction of winds found on all other, similar planets.

Speeding around their stars in orbits of three Earth days or less, hot Jupiters are tidally locked to the stars, with one side always facing the star and the other always facing away from it.

This results in their day sides being extremely hot. Winds blowing in an easterly direction transport heat to these planets' night sides, in some cases causing the hottest spots on the planets to be displaced in an eastward direction.

However, CoRoT-2b, a hot Jupiter approximately 930 light years away discovered about 10 years ago, has winds that blow in a westward rather than eastward direction, puzzling researchers.

The planet has other strange features, including an inflated size and an unusual spectrum of surface light emissions.

Researchers at McGill University's McGill Space Institute (MSI) and at the Institute for Research on Exoplanets (iREx), both in Montreal, observed CoRoT-2b with NASA's Spitzer Space Telescope and in the process discovered the "wrong way" wind.

"We've previously studied nine other hot Jupiter, giant planets orbiting super close to their star. In every case, they have had winds blowing to the east, as theory would predict," said Nicolas Cowan of McGill University.

"But now, nature has thrown us a curve ball. On this planet, the wind blows the wrong way. Since it's often the exceptions that prove the rule, we are hoping that studying this planet will help us understand what makes hot Jupiters tick."

The researchers used Spitzer's Infrared Array Camera (IRAC) to study the planet as it orbited its star, enabling them to map its surface brightness. Through this mapping, they found its hot spot, which is displaced in a westward direction.

"Both of these factors suggest there is something unusual happening in the atmosphere of this hot Jupiter," study leader Lisa Dang of McGill University said regarding the planet's inflated size and unusual light spectrum emissions.

In a study published in the journal Nature Astronomy, the researchers proposed several possible explanations for the strange wind direction.

One possibility is that the planet rotates very slowly, with a single rotation taking longer than a revolution around the star.

Alternatively, CoRoT-2b's magnetic field could be affecting its wind patterns by interacting with the planet's atmosphere.

A third possibility is that the eastern side of the planet appears darker than it should due to a heavy cloud cover.

The researchers anticipate the James Webb Space Telescope (JWST), which will have a mirror with 100 times Spitzer's collecting power and is scheduled for launch next year, will provide data that will answer their many questions about this mysterious system.

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