An article published in the journal “Nature Astronomy” reports the identification of the exoplanet WASP-193 b (Image created with Gencraft), a gas giant whose diameter is approximately 1.5 times Jupiter’s but with a mass that is only one-seventh of Jupiter’s. A team of researchers led by Khalid Barkaoui of the University of Liège, Belgium, used the WASP-South telescope of the Wide Angle Search for Planets (WASP) collaboration to locate WASP-193 b and then study its characteristics with other instruments. The combination of this exoplanet’s mass and density is really difficult to explain since no theory of planetary formation leads to a planet like this.
Exoplanets with a very low density are nothing new, so much so that they deserve nicknames such as “cotton candy planets” or “super puffs”. In the Kepler 51 system, there are three of them and the authors of a study on them published in the journal “The Astronomical Journal” in January 2020 suggested that those characteristics are linked to their young age.
After its detection, the exoplanet WASP-193 b was studied with the TRAPPIST-South and SPECULOOS-South telescopes and ESO’s HARPS and CORALIE spectrographs. The star WASP-193, about 1,200 light-years away from Earth and slightly more massive than the Sun, is older than the Sun with an age estimated at around 6.6 billion years. This means that WASP-193 b isn’t a newly formed exoplanet that will one day lose most of its atmosphere and become a mini-Neptune.
The exoplanet WASP-193 b is also much larger and more massive than the three super puffs in the Kepler 51 system. It’s close to its star, with a year lasting a bit more than 6 Earth days, so it’s heated up considerably. It’s possible that it formed further away from its star and then got closer, otherwise, it would have already lost at least part of its atmosphere due to the action of the stellar wind.
An analysis of the composition of the exoplanet WASP-193 b indicates that it’s made mainly of hydrogen and helium but that’s the only normal characteristic of this gas giant. For the rest, its characteristics are even stranger than those of other super puffs and this makes it even more difficult to find an explanation for its formation.
The very bloated atmosphere of the exoplanet WASP-193 b requires that there’s an energy source in its depths but it’s difficult to understand the mechanisms that led to the formation of such an anomalous planet. It’s for this reason that the researchers believe it’s necessary to continue studying this planet’s atmosphere. The James Webb Space Telescope was designed among other things to study the atmospheres of exoplanets and could offer valuable information on WASP-193 b’s atmosphere. New data would be invaluable to help the theoretical work necessary to obtain a model that describes the formation of a planet with those characteristics.
