Water vapour found at distant Neptune-sized planet

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SHAFAQNA (Shia International News Association)

In a technical feat, astronomers said Wednesday they had detected water vapour in the atmosphere of a planet the size of Neptune orbiting a star some 130 light years from Earth.

It is the smallest and coldest exoplanet — a world outside our Solar System — for which these vital signs have been measured.

Water vapour, along with copious amounts of hydrogen, was found in the atmosphere of HAT-P-11b, which whizzes around its star in a 4.9-day, egg-shaped orbit. HAT-P-11b is about four times the size of Earth and is among the smallest exoplanets discovered.

Atmospheres are telltales of a planet´s formation and a guide to what is happening on its surface.

But until now, scientists had only been able to scrutinise the atmospheres of large exoplanets — scorching-hot “gas giants” similar to, or even bigger than, our own Jupiter.

Neptune, the outermost acknowledged planet of our Solar System, is around a third of the size of Jupiter.

Astronomers use a method called transmission spectroscopy, with telescopes studying a planet´s atmosphere as it passes in front of its host star — relying on the fact that different gases absorb light at different wavelengths.

Four Neptune-sized planets have been studied before, but roiling clouds or a dusty haze skewed the view for spectroscopy.

HAT-P-11b, though, was luckily free of the problem.

Its atmosphere seems similar to those of the giant planets in our own Solar System — mostly hydrogen with trace amounts of heavier atoms like oxygen in the form of water vapour, said Eliza Kempton at Grinnell College in Iowa in a comment on the study published in the journal Nature.

The study research was conducted using NASA´s Hubble and Spitzer space telescopes.

The discovery that not all smaller exoplanets have clouds is good news, said Kempton.

It raises expectations for NASA´s new James Webb space telescope to be launched in 2018 with a larger mirror than Hubble´s.

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