Beta Pictoris B, a planet ten times the size of Jupiter, is the first exoplanet to ever have its rotational rate measured by astronomers. The super-massive planet has a day just eight hours along, according to astronomers.
At that rotational rate, a person standing on the equator of the planet would be racing around the world at 62,000 miles per hour, roughly 60 times faster than on Earth. Jupiter also rotates quickly, roughly once every 10 hours.
"It is not known why some planets spin fast and others more slowly, 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," Remco de Kok from Leiden Observatory and study co-author of the study, stated in a university press release.
The massive, quickly rotating world orbits its star 63 light years from Earth.
Astronomers measured the rotational rate of the planet using the Very Large Telescope (VLT), located in Chile. This facility houses four telescopes, each of which has a diameter of nearly 27 feet. The observatory can see objects in such detail, it could make out two separate headlights on an automobile parked on the moon.
Astronomers detected carbon monoxide in the atmosphere of Beta Pictoris b, from electromagnetic radiation emitted from the gas. As the planet rotates, the signal coming from the edge turning toward the Earth experiences a shift upward in frequency, similar to the sound of an approaching train. On the other side, the opposite Doppler shift occurs, like a train speeding away from an observer. By measuring the difference in these two frequencies, researchers were able to calculate the rotational rate of the planet.
"I think that maybe the most exciting aspect of this paper is the relative ease with which we performed these observations. It means that in the coming years we will be able to measure the spin velocity of a whole sample of young gas giant planets," Ignas Snellen of Leiden Observatory told Space.com.
The giant planet is young, still in the process of coalescing from a disk of gas left over from the formation of its companion star. As Beta Pictoris b ages, astronomers expect the planet to shrink. As it does, the rotational rate should speed up, like a twirling ice skater, bringing in her arms. In so doing, the length of the day on the giant world will become shorter.
