beecee

Helium Exo-Planet:

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https://phys.org/news/2018-12-helium-exoplanet-inflated-balloon.html

Helium exoplanet inflated like a balloon, research shows:

December 6, 2018, University of Exeter:

Astronomers have discovered a distant planet with an abundance of helium in its atmosphere, which has swollen to resemble an inflated balloon.

An international team of researchers, including Jessica Spake and Dr. David Sing from the University of Exeter, have detected the inert gas escaping from the atmosphere of the exoplanet HAT-P-11b—found 124 light years from Earth and in the Cygnus constellation.

Read more at: https://phys.org/news/2018-12-helium-exoplanet-inflated-balloon.html#jCp

the paper:

http://science.sciencemag.org/content/early/2018/12/05/science.aat5879

Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet:

Abstract

Stellar heating causes atmospheres of close-in exoplanets to expand and escape. These extended atmospheres are difficult to observe because their main spectral signature—neutral hydrogen at ultraviolet wavelengths—is strongly absorbed by interstellar medium. We report the detection of the near-infrared triplet of neutral helium in the transiting warm Neptune-mass exoplanet HAT-P-11b using ground-based, high-resolution observations. The helium feature is repeatable over two independent transits, with an average absorption depth of 1.08 ± 0.05%. Interpreting absorption spectra with 3D simulations of the planet’s upper atmosphere suggests it extends beyond 5 planetary radii, with a large scale height and a helium mass loss rate ≲ 3×105 g‧s−1. A net blue-shift of the absorption might be explained by high-altitude winds flowing at 3 km‧s−1 from day to night-side.

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supplementary article:

https://phys.org/news/2018-12-exoplanet-atmosphere-tail.html

the paper:

http://science.sciencemag.org/content/early/2018/12/05/science.aat5348

Edited by beecee

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That is interesting, a warm neptune like object is especially interesting. I wonder if it would lose it's hydrogen before the helium? That could result in a water world with a basically helium atmosphere... 

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