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Unfriendly exoplanet is stormy, blistering hot, and full of carbon monoxide

ESOcast 197 Light: GRAVITY uncovers stormy exoplanet skies

The GRAVITY instrument on the European Southern Observatory (ESO)’s Very Large Telescope Interferometer (VLTI) has observed its first exoplanet, HR8799e. GRAVITY analyzes the composition of distant planets using optical interferometry, which is where signals from different telescopes are combined to see objects in higher resolution that would be possible with any one telescope.

The planet studied in this case is orbiting a young main-sequence star called HR8799, which is located around 129 light-years from Earth in the constellation of Pegasus. The four telescopes of the Very Large Telescope were used in combination to form a “super-telescope” which was able to see light coming from the planet and distinguish this from light produced by the star that it orbits.

This wide-field image shows the surroundings of the young star HR8799 in the constellation of Pegasus. This picture was created from material forming part of the Digitized Sky Survey 2. The location of HR8799 is shown. ESO/Digitized Sky Survey 2. Acknowledgement: Davide de Martin

The planet HR8799e is a “super-Jupiter,” meaning it is bigger than Jupiter, but it also much younger than any of the planets in our Solar System. It is calculated to be around 30 million years old, making it a baby by exoplanet standards. The fact that it is so young means it is a useful target for studying how planets and planetary systems develop.

But if you were hoping to visit HR8799e to see it for yourself, you’re out of luck — the planet is “thoroughly inhospitable” according to the ESO. Greenhouse gases and energy leftover from its formation mean that the planet is heated to a toasty 1000 degrees Celsius (1832 degrees Fahrenheit) on its surface.

The atmosphere on HR8799e is unfriendly too, with high levels of carbon monoxide as well as clouds of iron and silicate dust. This composition suggests that the atmosphere is in a constant state of dramatic and violent storm. The research team were able to work out the composition of the atmosphere thanks to the detailed spectrum information gathered by GRAVITY.

“Our observations suggest a ball of gas illuminated from the interior, with rays of warm light swirling through stormy patches of dark clouds,” team leader Sylvestre Lacour, researcher CNRS at the Observatoire de Paris – PSL and the Max Planck Institute for Extraterrestrial Physics, said in a statement. “Convection moves around the clouds of silicate and iron particles, which disaggregate and rain down into the interior. This paints a picture of a dynamic atmosphere of a giant exoplanet at birth, undergoing complex physical and chemical processes.”

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