The weather on a "super-Earth" orbiting a star 40 light years away is the first to be detected outside our solar system
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| Researchers have predicted that it is set to remain cloudy and hot on the planet GJ 1214b for a long time to come |
Scientists have issued a weather forecast for a planet outside our solar
system for the first time, with the alien ''super-Earth'' orbiting a star 40
light years away set to remain cloudy and hot for the foreseeable future.
Using Hubble, they found exoplanet GJ 1214b has cloudy skies and is overcast all of the time, which would make forecasting pretty predictable - and boring.
Researchers have predicted that it is set to remain cloudy and hot on the planet GJ 1214b for a long time to come.
The world orbits very close to its ''red dwarf'' parent star, raising temperatures to a scorching 232C.
Using the Hubble Space Telescope to study light filtering through the planet's atmosphere, US astronomers determined that it is shrouded by high-altitude clouds.
What they are made of is still unknown, but computer simulations suggest they could be composed of potassium chloride or zinc sulphide dust.
Earlier studies of the planet were not able to tell whether it had clear or cloudy skies.
Now scientists are confident it is both hot and permanently overcast - a little like Venus in our own Solar System.
As was the case with Venus until the era of space probes, the cloud cover makes it impossible to know what the planet 's surface is like.
Super-Earths, planets having a mass between that of the Earth and Neptune, are believed to be among the most common in our galaxy, the Milky Way. GJ 1214b, whose star lies in the constellation Ophiuchus, is roughly 2.7 times larger than the Earth.
Dr Jacob Bean, leader of the University of Chicago astronomers - whose results appear in the journal Nature, said: ''I think it's very exciting that we can use a telescope like Hubble that was never designed with this in mind, do these kinds of observations with such exquisite precision, and really nail down some property of a small planet orbiting a distant star.''
The observations took up 96 hours of Hubble Telescope time spread over 11 months - the longest period ever devoted to studying a single exoplanet with the space telescope.
Dr Bean's team analysed near-infrared light from the planet each time it passed in front of, or ''transited'', its star, an event that occurs every 38 hours.
Writing in Nature, the scientists described the findings as an important milestone on the way to identifying potentially habitable Earth-like planets among the stars.
GJ 1214b was discovered in 2009 by the MEarth Project, which searched for planets transiting 2,000 red dwarfs, abundant stars dimmer than the Sun.
Follow-up observations suggested that the planet's atmosphere was either mostly composed of water vapour or dominated by hydrogen with high-altitude clouds.
The new study ruled out a cloud-free atmosphere of water, methane, nitrogen, carbon monoxide or carbon dioxide.
A ''flat'' signal from the Hubble data, lacking chemical fingerprints, indicated the presence of high altitude clouds of uncertain composition shielding what lay beneath.
The US space agency Nasa's 6.5 metre James Webb Space Telescope, due to be placed in orbit later this decade, is expected to reveal more information about exoplanet atmospheres.
''Looking forward, JWST will be transformative,'' said graduate student Laura Keidberg, another member of the University of Chicago team.
''The new capabilities of this telescope will allow us to peer through the clouds on planets like GJ 1214b. But more than that, it may open the door to studies of Earth-like planets around nearby stars.''
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