Now Spitzer maps a windy world

More hot news, quite literally, from beyond the solar system as astronomers create the first map of a planet around another star. The planet is a gas giant so the map is really charting features in its cloudtops including one prominent hotspot.

Don’t hold your breath for anything resembling Google Mars or Google Moon. However, scientists believe the technique will one day allow them to map rocky worlds that resemble the Earth.

The newly-mapped planet, a windy world labelled HD 189733b, lies 62 light-years away in the constellation of Vulpecula. Its study is another triumph for the Spitzer space telescope, which observes the sky with infrared eyes.

Heather Knutson, of Harvard University, is lead author of a paper about the research which appears in Nature this week. She said: “We are getting our first good look at a completely alien world. We felt a little like Galileo must have felt when he first glimpsed Jupiter through the eyepiece of his telescope.”

Knutson’s team were unable to see the planet’s disk itself as it is too far away. However, they measured changes in its brightness as it rotated and this allowed them to plot a simple brightness map. Knutson said: “We can see the changes in brightness as features in the planet’s atmosphere rotate into and out of view.”

The completed map is compiled from more than 250,000 separate measurements. It reveals a hot spot that is about twice the size of Jupiter’s Great Red Spot but considerably hotter at a scorching 1,700 F.

The planet is an incredibly windy place too. Co-author David Charbonneau, of the Harvard-Smithsonian Center for Astrophysics, said: “This planet has powerful jet streams. While Earth’s jet stream blows at around 200 miles per hour, the jet stream on HD 189733b may blow as fast as 6,000 miles per hour.”

Like many so-called “hot Jupiters”, the giant planet lies very close to its parent star, at a distance of only three million miles, and zips around it in a year lasting just 2.2 days. Spitzer can only map such large, hot worlds but astronomers believe a future observatory, the James Webb Space Telescope, will catch detail on Earth-like planets after it is launched in 2013.

The top image is an artist’s impression of the windy world in orbit around its star. The other shows a projection of the created map onto a sphere. Credit: Nasa/JPL-Caltech/Heather Knutson (CfA).

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