Gas planet 124 light years away inflates like a balloon – Xinhua | English.news.cn – Xinhua
WASHINGTON, Dec. 6 (Xinhua) — An international team of astronomers have discovered a hot helium-rich planet that inflates like a balloon.
The study, published on Thursday in the journal Science, reported the exoplanet with gaseous helium in an extended cloud that is escaping from the planet.
The planet, equivalent in size to Neptune or four times larger than the Earth, is located in the Cygnus constellation and 124 light years from Earth.
Scientists led by Swiss astronomers used a spectrograph called Carmenes, installed on the telescope in Spain and for the first time observed in detail how this gas was blown away from the planet’s day side to its night side at over 10,000 kilometer per hour.
It was hard to detect helium in the atmospheres of exoplanets because its signature lies in the infrared, out of range of most of the instruments used previously. Carmenes is capable to identify over 100,000 colors in the infrared.
The 550 Celsius warm planet called HAT-P-11b is twenty times closer to its star than the Earth from the Sun, according to the study.
“We suspected that this proximity with the star could impact the atmosphere of this exoplanet,” said Romain Allart, PhD student at University of Geneva and the first author of the study.
Jessica Spake, PhD Student at University of Exeter, said: “The observations show helium being blasted away from the planet by radiation from its host star.”
“Because it is such a light gas, it escapes easily from the attraction of the planet and forms an extended cloud all around it,” said Vincent Bourrier, co-author of the study and member of the European project FOUR ACES, a study on upper atmosphere of exoplanets.
Helium is the second most common element in the universe and was long predicted to be one of the most readily-detectable gases on giant exoplanets. However, it was only successfully found in an exoplanet atmosphere earlier this year by a team led by Spake.
“Hopefully we can use this new study to learn what types of planets have large envelopes of hydrogen and helium, and how long they can hold the gases in their atmospheres,” said Spake.