The REAL 8 hour day! Scientists calculate rate of exoplanet's spin for the first time - and it rotates at a dizzying 62,000 mph
comments
The length of a day on a planet outside our solar system has been measured by scientists for the first time.
The planet, 63 light years from Earth, takes only eight hours to orbit its young star Beta Pictoris in the faint southern hemisphere constellation of Pictor - deriving from the Latin phrase for the 'painter's easel'.
This means it has a spinning speed of 62,100 mph (100,000 km/h) - much quicker than any planet in the solar system.
Scroll down for video...
This artist's view shows the planet orbiting the young star Beta Pictoris. This exoplanet is the first to have its rotation rate measured. Its eight-hour day corresponds to an equatorial rotation speed of 62,100 mph (100,000 km/h) - much faster than any planet in the solar system
BETA PICTORIS B
Only 12 million years old, or less than three-thousandths of the age of the sun, Beta Pictoris is 75 per cent more massive than our parent star.
It is located about 60 light-years away towards the constellation of Pictor (the Painter) and is one of the best-known examples of a star surrounded by a dusty debris disc.
It circles its host star at only eight times the distance of the Earth and the sun distance - making it the closest exoplanet to its star ever to be directly imaged.
Earlier observations showed a warp of the disc, a secondary inclined disc and comets falling onto the star, all indirect, but tell-tale signs that strongly suggested the presence of a massive planet.
By comparison Jupiter's equator has a velocity of about 29,200 mph (47,000 km/h) while the Earth's travels at only 1,050 mph (1,700 km/h).
Despite its short day Beta Pictoris b is more than 16 times larger and has a mass 3,000 times greater than the Earth.
The gas-giant discovered in 2008 is more than one-and-a-half times the size of Jupiter and still very young and warm - only 20 million years old compared to 4.5 billion years for Earth.
It circles its host star at only eight times the distance of the Earth and the sun distance - making it the closest exoplanet to its star ever to be directly imaged.
Beta Pictoris b is a giant planet - several times larger than Jupiter - and is approximately ten million years old. This near-infrared image show the planet glowing in infrared light from the heat released in its formation. The bright star Beta Pictoris is hidden behind a mask in the centre of the image
Dr Remco de Kok, of the Netherlands Institute for Space Research in Utrecht, said: 'It's not known why some planets spin fast and others more slowly but this first measurement of an exoplanet's rotation shows 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.'
Over time Beta Pictoris b is expected to cool and shrink which should make it spin even faster. On the other hand other processes could change the spin of the planet.
For instance the spin of the Earth is slowing down due to tidal interactions with our Moon.
Using the Very Large telescope in the Chilean Andes the Dutch astronomers relied on a precise technique called high-dispersion spectroscopy to split light into its constituent colours - different wavelengths in the spectrum.
The principle of the Doppler shift - a change in frequency in wavelengths - allowed them to detect different parts of the planet were moving at different speeds and in opposite directions relative to the observer.
Using the Very Large telescope in the Chilean Andes the Dutch astronomers relied on a precise technique called high-dispersion spectroscopy to split light into its constituent colours - different wavelengths in the spectrum. Using this data they were able to extract the rotation signal from the planet
By very carefully removing the effects of the much brighter parent star they were able to extract the rotation signal from the planet.
Professor Ignas Snellen, of Leiden University, said: '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 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.'
This technique is closely related to Doppler imaging which has been used for several decades to map the surfaces of stars - and recently that of the brown dwarf Luhman 16B less than seven light years away where it rains molten iron.
The fast spin of Beta Pictoris b means in future it will be possible to make a global map of the planet - showing possible cloud patterns and large storms.
The researchers whose study is published in Nature hope to use the technique on a much larger sample of exoplanets and characterise much smaller ones than Beta Pictoris b.
Put the internet to work for you.
0 comments:
Post a Comment