Giant exoplanets orbiting very close to their parent star ( hot Jupiters ) are subject to tidal forces expected to synchronize their rotational and orbital periods on short timescales ( tidal locking ) .
However , spin rotation has never been measured directly for hot Jupiters .
Furthermore , their atmospheres can show equatorial super-rotation via strong eastward jet streams , and/or high-altitude winds flowing from the day- to the night-side hemisphere .
Planet rotation and atmospheric circulation broaden and distort the planet spectral lines to an extent that is detectable with measurements at high spectral resolution .
We observed a transit of the hot Jupiter ( catalog HD 189733 b ) around 2.3 µm and at a spectral resolution of R \sim 10 ^ { 5 } with CRIRES at the ESO Very Large Telescope .
After correcting for the stellar absorption lines and their distortion during transit ( the Rossiter-McLaughlin effect ) , we detect the absorption of carbon monoxide and water vapor in the planet transmission spectrum by cross-correlating with model spectra .
The signal is maximized ( 7.6 \sigma ) for a planet rotational velocity of ( 3.4 ^ { +1.3 } _ { -2.1 } ) km s ^ { -1 } , corresponding to a rotational period of ( 1.7 ^ { +2.9 } _ { -0.4 } ) days .
This is consistent with the planet orbital period of 2.2 days and therefore with tidal locking .
We find that the rotation of HD 189733 b is longer than 1 day ( 3 \sigma ) .
The data only marginally ( 1.5 \sigma ) prefer models with rotation versus models without rotation .
We measure a small day- to night-side wind speed of ( -1.7 ^ { +1.1 } _ { -1.2 } ) km s ^ { -1 } .
Compared to the recent detection of sodium blue-shifted by ( 8 \pm 2 ) km s ^ { -1 } , this likely implies a strong vertical wind shear between the pressures probed by near-infrared and optical transmission spectroscopy .