Two-faced world: One of a series of computer-generated images charting the development of severe weather patterns on the exoplanet HD 80606b. The blue glow of the crescent is starlight that has been scattered and reflected by planet. The night side appears reddish orange as it glows with its own internal heat.
Credit: NASA/JPL-Caltech/UCSC
PARIS: Astronomers have observed a planet some 200 light-years from Earth that, for a few hours, becomes 700 ºC hotter every time its elliptical orbit brings it close to its sun.
In a study today in the British journal Nature, the scientists say they have generated the most realistic images ever captured of an exoplanet.
Hotter than molten lava
They used infrared data collected from NASA's space-based Spitzer telescope to gain pictures of a strange world exposed briefly to a raging inferno. The computer generated images show a thin blue crescent on the side of the planet illuminated by the star, while the dark side glows red with the planet's own internal heat.
Known as HD 80606b, the planet is a giant ball of gas that has four times the mass of Jupiter, the biggest planet of our system.
Researchers led by Gregory Laughlin of the University of California in Santa Cruz, U.S., analysed data collected in November, hours before, during and after HD 80606b's closest approach to its star.
From the telescope's vantage point, the planet passed behind the star – an event called a secondary eclipse – just before reaching its maximum temperature of around 1,230 ºC, hotter than molten lava. It was an unexpected stroke of luck, making it possible to measure the exact temperatures of the star and the planet separately.
Alien weather system
"This is the first time that we've detected weather changes in real time on a planet outside our Solar System," said Laughlin. "The results are very exciting because they give us important clues to the atmospheric properties of the planet."
As the atmosphere heats up and expands, it produces fierce winds – moving at five kilometres per second – that flow away from the day side toward the night side. The planet's rotation causes the winds to curl up into large-scale storm systems that gradually peter out as temperatures cool, Laughlin said.
HD80606b swings around its sun in an elliptical orbit every 111.4 Earth days.
It is one of about a dozen so-called "hot Jupiter" extrasolar planets which spin on their axes in such a way that the same surface is always facing their respective stars.
