Astronomers finally have an idea of what it's like to spend a day in an exoplanet. For the first time in history, scientists stationed at the Very Large Telescope in Chile have clocked the length of an exoplanet's day.

European Southern Observatory (ESO) astronomers observing an exoplanet known as 'Beta Pictoris b' have worked out that the planet experiences days that are only around eight hours long. Like Jupiter, the gas giant also spins at a very fast rate. In terms of speed however, Beta Pictoris b rotates even faster. The astronomers who made the observation published their findings in the online journal Nature.

While this is considered as the first time that an exoplanet's day has been measured, the scientists working on the study say that the process was surprisingly easy. The team used a technique that involved combining high-contrast images and highly accurate spectroscopy to measure the length of the exoplanet's day. However, scientists are still trying to understand the reasons behind some exoplanets rotating faster than others.

"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," said ESO astronomer and study co-author Remco de Kok.

Spectroscopy involves breaking down light into different wavelengths and using chemical analysis to gather more information about the light source. The team found evidence of carbon monoxide in the atmosphere of Beta Pictoris b. By analyzing the traces of carbon monoxide, the astronomers were able to measure the rate at which the planet was spinning. When a planet spins, the carbon monoxide in its atmosphere is also agitated. By studying the movement of the gas, the scientists were able to determine that the planet was rotating at a speed of 15.5 miles per second.

"This technique can be used on a much larger sample of exoplanets with the superb resolution and sensitivity of the E-ELT and an imaging high-dispersion spectrograph. With the planned  Mid-infrared E-ELT Imager and Spectrograph (METIS) we will be able to make global maps of exoplanets and characterise much smaller planets than Beta Pictoris b with this technique," said Bernhard Brandl, the Mid-Infrared E-ELT Imager and Spectrograph (METIS) principal investigator and one of the co-authors of the paper.

Astronomers believe that Beta Pictoris b is still a relatively young planet. Due to its apparent "youth," the planet is still warm. However, scientists say that the planet will eventually cool down after a few hundred million years.

While little is currently known about the mechanisms behind the rate at which a planet rotates, the latest discovery supports previous theories that a planet's rate of rotation is somehow related to the planet's total mass. This can also be observed within the Solar System where gas giants such as Jupiter and Saturn rotate at impressive speeds. With the data gathered from Beta Pictoris b however, scientists now have extra-solar evidence to support the theory.

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