Half-Hot, Half-Cold Planets Have Supersonic Jet Streams

October 20, 2008

Jupiter-like exoplanets—planets outside our solar system—have supersonic jet streams that transport heat from their sunny side to their dark side, a new study says.

These gas giants orbit extremely close to nearby stars.

"Because these planets are so close to their stars, we think they're tidally locked, with one side permanently in starlight and the other side permanently in darkness," said lead study author Adam Showman, a planetary scientist of the University of Arizona.

"So, if there were no winds, the dayside [the side of a planet in sunlight] would be extremely hot, and the nightside would be extremely cold."

But when the winds pick up, they bring scorching heat—sometimes even on the cool side—that's hotter than anything seen in our own solar system.

The exoplanets "are pretty crazy places. Expect supersonic winds and dayside temperatures hot enough to melt lead and rocks," Showman said in a statement.

(Related: "First Proof of Wet 'Hot Jupiter' Outside Solar System" [July 11, 2007].)

The work was presented recently at the annual meeting of the American Astronomical Society's Division for Planetary Sciences, and will appear in an upcoming issue of the Astrophysical Journal.

Extreme Heat

Showman and colleagues combined Spitzer and Hubble space telescope observations with computer models to puzzle together weather and climate patterns on the gas giants.

About 300 Jupiter-like planets have been discovered around stars, and, in most cases, astronomers know their masses and orbits.

For a handful of the brightest planets, space-based telescopes such as Spitzer have sent back images that reveal surface temperatures.

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