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The GRAVITY instrument on ESO's Very Large Telescope Interferometer (VLTI) has made the first direct observation of an exoplanet using optical interferometry. This method revealed a complex exoplanetary atmosphere with clouds of iron and silicates swirling in a planet-wide storm. The technique presents unique possibilities for characterising many of the exoplanets known today © ESO/L. Calçada

Planet-wide storm discovered on alien world

Published: 07th April, 2019 at 08:00
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Astronomers have used a “super-telescope” to discover a violent storm raging on an alien planet some 129 light-years away from Earth.

Astronomers have used a “super-telescope” to discover a violent storm raging on an alien planet some 129 light-years away from Earth.


The team studied this planet, with the catchy name HR8799e, using the Very Large Telescope (VLT) in Chile. The VLT is composed of four individual telescopes, each of which is over eight metres in diameter. These four can be used together, effectively forming one much bigger telescope.

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Bigger is better when it comes to astronomy: the bigger the telescope, the sharper the image. Astronomers combine telescopes in a process known as interferometry to study objects that are too far away to observe with just one telescope. When the telescopes collect light in the range that human eyes can see, this is called optical interferometry.

This is the first time that optical interferometry has been used to study an exoplanet, and it revealed more detail about the HR8799e’s atmosphere than any previous observations. The astronomers, led by Sylvestre Lacour at the Observatoire de Paris, analysed the wavelengths of light emitted by the planet to deduce what gases could be found in its atmosphere.

Aerial view of the VLTI with tunnels superimposed © ESO

“Our analysis showed that HR8799e has an atmosphere containing far more carbon monoxide than methane,” said Lacour. This is unusual since methane is created when carbon monoxide reacts with hydrogen, which is the most abundant element in the Universe. Something must be stopping that reaction from taking place, and the team believe that strong winds would do the trick.

As well as an abundance of carbon monoxide, HR8799e’s atmosphere has clouds of iron particles and silicates. For all of these to exist in the atmosphere together, the astronomers believe that a violent storm must be stirring up the clouds. “This paints a picture of a dynamic atmosphere of a giant exoplanet at birth, undergoing complex physical and chemical processes,” Lacour explained.

HR8799e was discovered in 2010, the fourth and innermost found around its host star, which is a young star, 129 light-years from Earth. Even without its tempestuous weather, it would be an uninhabitable planet: it is a gas giant with a temperature that soars to at least 1,000°C.

It’s hoped that this tool will help astronomers to make many more discoveries on alien worlds.


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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.


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