Fluffier than Cotton Candy: The Enigma of Exoplanet WASP-193b

A group of scientists from the University of Liège in Belgium reported in "Nature Astronomy" about discovering an exoplanet about 7,460 light-years away from Earth. Its density is similar to that of cotton candy. WASP-107b is one of the lightest gas giants ever discovered.

WASP-193b, as the newly discovered planet was named, is more significant than Jupiter by half, but it is seven times lighter. The dominance of hydrogen and helium in its composition means it has an extremely low density, comparable to cotton candy. This is exceptionally rare. So, how can the stable existence of such a planet be explained?

Khalid Barkaoui, the publication's lead author, stated that WASP-139b is the second least dense planet identified so far, right after Kepler-51d, which, however, is much smaller. He also noted that its extremely low density is somewhat of an anomaly among the over five thousand exoplanets identified. He emphasized that it is difficult to explain such a low density using standard models of irradiated gas giants, even assuming the most optimistic scenarios and a lack of an internal core.

This discovery was made possible thanks to the international Wide Angle Search for Planets (WASP) study. Researchers used automated telescopes located around the world, which provided the right conditions for identifying the planet. It was determined that WASP-193b completes a full orbit around its parent star, WASP-193, within approximately 6 days.

The team from the University of Liège utilized the TRAPPIST-South, SPECULOOS-South observatories and the European Southern Observatory, located in Chile, in their research. The density of WASP-193b turned out to be only 0.105 grams per cubic centimetre (approximately 0.002 ounces per cubic inch). For such a giant planet, this is incredibly rare. In comparison, Jupiter, the most massive planet in our Solar System, has a density of about 1.33 grams per cubic centimetre (approximately 0.024 ounces per cubic inch). Scientists have pointed out that the only material with a density comparable to this exoplanet is cotton candy.

The reason this planet has a density comparable to cotton candy lies in the structure of both materials. While cotton candy is almost entirely made up of air, this planet is incredibly fluffy. That's how the scientists explain it.

Experts emphasize that WASP-193b is mainly composed of hydrogen and helium, typical for gas giants. However, in this case, these gases form an extensive atmosphere that stretches much further than Jupiter's atmosphere. We are not able to explain this today, using all existing theories.

Researchers believe that ensuring stability to this planetary structure requires significant internal energy. However, no one knows the source of this energy.

Dr. Barkaoui summarized that WASP-193b is a cosmic mystery requiring further observational and theoretical research. To understand this phenomenon, a detailed analysis of the atmosphere, possible thanks to the James Webb Telescope, and its comparison with theoretical mechanisms that could explain its inflation are necessary.