Unearthly blue: Scientists reveal color of planet 63 light years away

Unearthly blue: Scientists reveal color of planet 63 light years away
For the first time, astronomers have been able to determine the color of a planet outside the solar system, and it turns out that this planet is blue. It circles a star 63 light years away from Earth, and it rains melting glass there.

The planet is 13 percent bigger than Jupiter, and orbits very close to its star, circling it once in 2.2 days.

The ‘deep blue’ planet belongs to the ‘hot Jupiter’ gas giant planet type, but is much hotter than the largest planet in our solar system: cloud temperatures are likely to measure almost 1,000 degrees Celsius (1,800 degrees Fahrenheit).

Winds sweep the planet at speeds of over 7,200kph (4,350mph).

"Measuring its color is a real first - we can actually imagine what this planet would look like if we were able to look at it directly," said Frederic Pont of the University of Exeter, who co-wrote the paper in The Astrophysical Journal Letters.

"As far as I am aware, nobody has had actual results on the color of an exoplanet," Pont said. "Now we can say that this planet is blue."

The color of HD 189733b compared to our solar system. Credit: NASA, ESA, and A. Feild (STScI/AURA)

Its clouds are also blue, according to the data from the Hubble telescope, used by an international team of astronomers. The group observed the planet before, during and after it was eclipsed by its star, which allowed them to subtract the light from the star from the light reflected off the planet, giving them a sense of its color.

"We saw the brightness of the whole system drop in the blue part of the spectrum when the planet passed behind its star," Evans says, in a statement. "From this, we can gather that the planet is blue, because the signal remained constant." 


Astronomers suggest that the blue color comes from a hazy atmosphere filled with small particles of glass – and it actually rains melting glass on the planet.

The blue planet is situated 63 light years (around 600 trillion km) from the Earth, and is called HD 189733b. It was discovered in 2005.

The most recent findings on the planet’s color have been published in the latest issue of the Astrophysical Journal Letters.

The planet is only 2.9 million miles from its parent star, so close that it is gravitationally locked, NASA says. One side always faces the star and the other side is always dark.

By contrast, Mercury, the closest planet in our solar system to the sun, is 29 million miles away from the sun at its closest point of orbit.

Exotic blue planet HD 189733b (labelled artist’s impression). Credit: NASA, ESA, and G. Bacon (AURA/STScI)