Washington, May 1
Do you know that an exoplanet has a day that lasts only eight hours – much quicker than any planet in the solar system as its equator is moving at almost 100,000 kms per hour?
Observations from European Southern Observatory’s Very Large Telescope (VLT) have, for the first time, determined the rotation rate of an exoplanet ‘Beta Pictoris b’ that has been found to have a day that lasts only eight hours.
It is not known why some planets spin fast and others more slowly.
“This first measurement of an exoplanet’s rotation shows that the trend seen in the solar system also holds true for exoplanets. This must be some universal consequence of the way planets form,” explained co-author Remco de Kok.
This new result extends the relation between mass and rotation seen in the solar system to exoplanets.
In this case, ‘Beta Pictoris b’ is a very young planet, only about 20 million-years old (compared to 4.5 billion years for the earth).
This planet was discovered nearly six years ago and was one of the first exoplanets to be directly imaged.
Over time, the exoplanet is expected to cool and shrink, which will make it spin even faster.
“On the other hand, other processes might be at play that change the spin of the planet. For instance, the spin of the earth is slowing down over time due to the tidal interactions with our moon,” astronomers said.
During the study, the astronomers made use of a precise technique called high-dispersion spectroscopy to split light into its constituent colours – different wavelengths in the spectrum.
This technique is closely related to Doppler imaging which has been used for several decades to map the surfaces of stars.
“The new technique can be used on a much larger sample of exoplanets with the superb resolution,” said Bernhard Brandl, principal investigator of Mid-infrared E-ELT Imager and Spectrograph (METIS).
Similar techniques will allow astronomers to map exoplanets in detail in the future with the European Extremely Large Telescope (E-ELT), he said.