Duration Of An Exoplanetary Day Measured For The First Time

A distant Jupiter-like world has been shown to feature the fastest rotational speed ever observed in a planet.

Called Beta Pictoris b, it's a gas giant that's located 63 light-years from Earth and about 10 times more massive than Jupiter. Observations from the ESO's Very Large Telescope (VLT) determined its rotation rate — a blistering 62,000 mph (100,000 km/hr) at the equator, so its day is only eight hours long.

Yes, that's a really short duration compared to, say, the Earth's 24 hours, but we're rotating at a modest 1,060 mph (1,700 km/hr). Beta Pictoris b is markedly larger than our solar system's largest planet, Jupiter — by comparison, Jupiter's equator spins around at about 29,000 mph (47,000 km/h), featuring a day that's 10 hours long.

"It is not known why some planets spin fast and others more slowly," noted co-author Remco de Kok in an ESO statement, "but this first measurement of an exoplanet's rotation shows that the trend seen in the Solar System, where the more massive planets spin faster, also holds true for exoplanets. This must be some universal consequence of the way planets form."

At 20-million-years-old, Beta Pictoris b is a young planet — but over time, it's expected to cool and shrink, which will make it spin even faster.

[ Source: ESO ]

Image: ESO L. Calçada/N. Risinger.