Artist’s impression of the exoplanet HAT-P-11b. Image Credit: Denis Bajram

Scientists Find Mysterious Alien Planet that Looks Like a Balloon

Now this is one crazy-looking planet in outer space.


The Curious Case of the Helium-Inflated Exoplanet

Astronomers have uncovered one of the most peculiar alien worlds yet: a Neptune-sized exoplanet with an atmosphere filled with helium. Located approximately 124 light-years away from Earth in the constellation of Cygnus, this distant planet, dubbed HAT-P-11b, has an odd balloon-like shape due to its helium-rich atmosphere.

Helium Leakage: A Cosmic Phenomenon

The international team of astronomers, led by the University of Geneva, found that helium is leaking from the planet’s atmosphere, similar to how a helium balloon might escape from a person’s hand. Dr. Jessica Spake, from the University of Exeter’s physics and astronomy department, expressed her excitement over the discovery, as helium had only been detected in exoplanet atmospheres for the first time earlier this year.


Dr. Spake explains that the observations show helium being blasted away from the planet by radiation from its host star. She hopes that this new study can help scientists learn more about what types of planets have large envelopes of hydrogen and helium and how long they can retain these gases in their atmospheres.


Studying the Helium Cloud with Advanced Techniques

To investigate HAT-P-11b, astronomers utilized a spectrograph in Spain, enabling them to measure how much light the planet blocks from its host star as it passes in front of it. By breaking down the star’s light into component colors, like a rainbow, and considering helium’s absorption of light at a specific wavelength, they were able to detect a large cloud of gas surrounding the planet that blocked more light than the planet itself.

Computer simulations were employed to track the helium atoms’ trajectory. Vincent Bourrier, who led the simulation, explains that helium is blown away from the planet’s dayside to its night side at over 10,000 kph. As a light gas, helium easily escapes the planet’s gravitational pull, forming an extended cloud around it.

Implications of the Balloon-like Exoplanet

Romain Allart, a Ph.D. student at the University of Geneva and the study’s first author, suggests that the exoplanet’s close proximity to its host star impacts its atmosphere. The new observations are so precise that it’s undeniable that the exoplanet’s atmosphere is inflated by stellar radiation and escapes into space.


This intriguing discovery of the helium balloon planet expands our understanding of the diversity of exoplanets and their atmospheres. As researchers continue to explore the vastness of the cosmos, the detection of unique worlds like HAT-P-11b highlights the boundless possibilities of what lies beyond our own solar system.

Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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