Exoplanet Beta Pictoris b has 8 Hour Days

Posted on April 30, 2014

Astronomers have determined that exoplanet Beta Pictoris b has 8 hour days. This is the first time the length of exoplanet day has been measured. The equatorial rotation velocity of Beta Pictoris b is nearly 100,000 kilometers per hour (about 62,137 mph). The observations were made from ESO's Very Large Telescope (VLT).

Beta Pictoris b is located about 63 light-years from Earth in the constellation Pictor. The young planet is estimated to be 20 million years old. It was discovered six years ago and was one of the first planets to be directly imaged. An artist's impression of the planet is pictured above.

The astronomers used a technique called high-dispersion spectroscopy to split light into different wavelengths in the spectrum. They then used the Doppler effect principle to use changes in wavelength to detect that different parts of the planet were moving at different speeds and in opposite directions relative to the observer. By removing the effects of the much brighter parent star they were able to extract the rotation signal from the planet.

Ignas Snellen from Leiden University, lead author of the study, says, "We have measured the wavelengths of radiation emitted by the planet to a precision of one part in a hundred thousand, which makes the measurements sensitive to the Doppler effects that can reveal the velocity of emitting objects. Using this technique we find that different parts of the planet's surface are moving towards or away from us at different speeds, which can only mean that the planet is rotating around its axis."

The research was published here in the journal Nature. The Nature article says astronomers expect the planet's rotation to speed up even more as it cools and shrinks. Eventually it will have a sunset every three hours.

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