A group of scientists have become the first to determine the colour of a planet outside the solar system – and it has an identical haze to Earth.
Boffins using the NASA/ESA Hubble Space Telescope have discovered that the planet, known as HD 189733b, is a deep cobalt blue.
It is the first time astronomers have managed to identify the colour of an exoplanet which, in this case, is caused by an atmosphere laced with silicate particles that scatter blue light.
But matching colours are the only similarities between Earth and HD 189733b, with the violent exoplanet completely inhospitable.
The planet, which was discovered in 2005, is known as a ‘hot Jupiter’ because of its similarity to the giant gas planet in the solar system.
Temperatures are in excess of 1,000 degrees celsius and it rains GLASS in 7,000kph winds.
The exoplanet is 63 million light years away from Earth – with each light year representing a staggering six TRILLION miles.
Despite being an enormous distance from Earth, HD 189733b is one of the nearest exoplanets which can be seen crossing the face of its star.
The planet circles its star at a distance of three million miles, or about 30 times closer than Earth’s distance from the sun, and completes an orbit every 2.2 days.
It has been intensively studied by Hubble and other telescopes, and its atmosphere has been found to be dramatically changeable and exotic, with hazes and violent flares.
Frédéric Pont, from the University of Exeter, was one of the scientists behind the colour discovery, which is documented in the August issue of the journal Astrophysical Journal Letters.
He said: “This planet has been studied well in the past, both by ourselves and other teams.
“But measuring its colour is a real first – we can actually imagine what this planet would look like if we were able to look at it directly.
“It’s difficult to know exactly what causes the colour of a planet’s atmosphere, even for planets in the Solar System.
“But these new observations add another piece to the puzzle over the nature and atmosphere of HD 189733b. We are slowly painting a more complete picture of this exotic planet.”
To work out the planet’s colour, the team measured how much light was reflected off its surface.
They used Hubble’s Space Telescope Imaging Spectrograph to peer at the system before, during, and after the planet passed behind its host star as it orbited.
Tom Evans of the University of Oxford, added: “We saw the brightness of the whole system drop in the blue part of the spectrum when the planet passed behind its star.
“From this, we can gather that the planet is blue, because the signal remained constant at the other colours we measured.”
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