Distant Exoplanet Is Inflated Like A Balloon

Researchers have detected an extended helium cloud around HAT-P-11b that is escaping from the planet.

Astronomers have found a distant planet with an abundance of helium in its atmosphere. The newly discovered exoplanet is losing its atmosphere in the form of an extended cloud of helium. The helium cloud looks like a balloon that may have escaped from a person’s hand.

“This is a really exciting discovery, particularly as helium was only detected in exoplanet atmospheres for the first time earlier this year. The observations show helium being blasted away from the planet by radiation from its host star. 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.” Jessica Spake from University of Exeter said.

The helium-filled exoplanet HAT-P-11b is located 124 light years from Earth and in the Cygnus constellation. Helium is the second most common element in the universe. But it is only the second time researchers have found an exoplanet enriched with helium. The same team revealed an abundance of helium in the upper atmosphere of a super-Neptune exoplanet earlier this year, which was only discovered in 2017.

To detect the atmosphere of exoplanet HAT-P-11b, researchers used the spectrograph Carmenes, which is installed on the 4-metre telescope at Calar Alto, Spain. The spectrograph has made it possible to reveal the composition of the atmosphere of this exoplanet and the position and speed of helium atoms in the upper atmosphere that leave the gravitational field of the planet and create an extended cloud. New observations showed that the exoplanet’s atmosphere is likely influenced by the stellar radiation and the phenomenon makes HAT-P-11b so inflated, like a helium balloon.

“Helium is blown away from the day side of the planet to its night side at over 10,000 km an hour. Because it is such a light gas, it escapes easily from the attraction of the planet and forms an extended cloud all around it.” Co-author Vincent Bourrier said.

The ground-breaking study suggests that the formation processes of exoplanets can be very different from that of other planets outside our solar system. The discovery could pave the way for scientists to study extreme atmospheric conditions found around other exoplanets.