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A planet with 4,500-m.p.h. winds? Now that's a superstorm.

Scientists have succeeded in clocking the winds in the atmosphere of a planet orbiting a star in the constellation Pegasus. Windiest planet in our solar system is Neptune, at 1,200 m.p.h.

By Staff writer / June 23, 2010

This artist's impression shows the Jupiter-like planet HD 209458b transiting around its sun-like host star, some 150 light-years away. For the first time, astronomers have measured a superstorm in the atmosphere of a planet outside our solar system.



If you're planning a trip to planet HD 209458b (not recommended for several reasons), hold on to your hat. Astronomers have just clocked the planet's high-altitude winds at a hair less than 4,500 miles per hour.

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"Measured winds on Jupiter and Saturn are only a fraction of this," notes Leiden University astronomer Ignas Snellen, who led a team of researchers probing the extrasolar planet's traits. The closest competitor our solar system can offer up is Neptune, with winds speeds estimated as high as 1,200 m.p.h.

The measurement, reported in Wednesday's issue of the journal Nature, in effect was a byproduct of efforts to look at a now-familiar extrasolar planet with sharper eyes, adds team member and astronomer Simon Albrecht.


In this case, the team was using a relatively new spectrograph at the European Southern Observatory's Very Large Telescope array in Chile to confirm previous observations and see what more the spectrograph might reveal.

The results "were more than we hoped for," says Dr. Albrecht, who splits his time between Leiden University and the Massachusetts Institute of Technology. Not only was the team able to detect wind speeds on a planet 150 light-years away. But the scientists were also able to measure the pace of its orbit with far higher precision, which in turn allowed them to make simpler, more direct calculations of the planet's mass than predecessors have been able to use.

The effort highlights the increasingly detailed information astronomers are gathering as they aim giant ground-based telescopes at some of the extrasolar planets nearest our solar system.

So far, astronomers have found 463 planets outside the solar system. The latest discoveries were unveiled last week, when scientists using the French CoRoT satellite added six planets to the extrasolar planet catalog.

HD 209458b a 'hot Jupiter'

Meanwhile, the National Aeronautics and Space Administration's Kepler mission last week released its first 43 days' worth of data on some 156,000 stars in the vicinity of the constellations Cygnus and Lyra. The team is paying special attention to some 400 of these stars in hopes of detecting planets orbiting them.

Many of the extrasolar planets discovered are so-called hot Jupiters – gas giants that orbit very close to their parent star.

Among these hot Jupiters, none has come under as close scrutiny as HD 209458b, which orbits a star in the constellation Pegasus. Astronomers discovered the planet in 1999, and it's been a target for ground- and space-based telescopes ever since.

The man reason: Its star is relatively close to Earth and very bright, making the system easier to observe in a relatively short period of time.