Scientists have for the first time measured the rotation of a planet in another solar system – a juvenile, gassy giant spinning at a breakneck 90,000km/h.
Orbiting a star about 63 light years from Earth, Beta Pictoris b is more than 16 times larger and 3000 times more massive than our planet, but its days last only eight hours.
“Beta Pictoris b spins significantly faster than any planet in the solar system” – at a rate of about 25 kilometres per second (90,000km/h), a team of Dutch astronomers wrote in the journal Nature.
Jupiter’s equator turns at about 47,000km/h and that of Earth at 1700km/h.
The measurement, done with the European Southern Observatory’s Very Large Telescope, echoes a trend observed in our own solar system of increasing spin velocity with higher planet mass.
This association would predict an even faster spin of about 50km/s for Beta Pictoris b, but the team noted the planet was still young and warm and would likely pick up speed as it cools and shrinks to the size of Jupiter in the coming hundreds of millions of years.
The planet orbits the star Beta Pictoris in the southern constellation of Pictor (The Painter’s Easel).
Discovered nearly six years ago, it orbits its star at a distance eight times that of the Earth to the sun.
Beta Pictoris b is about 20 million years old – very young in astronomical terms, compared to the Earth’s 4.5 billion years.
The astronomers used a technique called high-dispersion spectroscopy to measure changes in the wavelengths of radiation emitted by the planet and so determine its spin velocity.