How strange does a planet have to be to be compared to cotton candy? An international team of astronomers has just discovered WASP-193b, a gas giant so fluffy that it challenges our current understandings of the universe. WASP-193b is not your average planet. It is 50% larger than Jupiter, but seven times less massive. Its density is so low that it could float on water: a true cosmic anomaly. It orbits its star every 6,25 days, a very short period that contributes to its expansion.
A mystery for scientists
I'll put it very simply: current theories of planetary formation cannot explain a planet like this. “WASP-193b is the second least dense planet discovered to date, after Kepler-51d, which is much smaller,” he said Dr Khalid Barkaoui, researcher at the University of Liège. “Its extremely low density cannot be reproduced by standard models of irradiated gas giants, even assuming a coreless structure.”
The observations (that I link to you here) estimated that WASP-193b It has a density of 0,059 grams per cubic centimeter. For comparison, water has a density of 1 gram per cubic centimeter, so WASP-193b would float on water. In the Solar System, only Saturn has a lower density than water, at 0,687 grams per cubic centimeter. Jupiter, however, is much denser at 1,33 grams per cubic centimeter, and Earth far surpasses both at 5,51 grams per cubic centimeter.
The strangeness of a fluffy giant
Defining WASP-193b a “gas giant” seems almost reductive. Its lightness is so extreme that there is no similar solid material on Earth.
The planet is so light that it is difficult to think of an analogous solid material. The reason it is compared to cotton candy is that both are basically air. The planet is basically super soft.
Julien de Wit, professor at MIT.
“We don't know where to place this planet in all current formation theories, because it is an anomaly compared to all of them,” he added Francisco Pozuelos, astronomer at the Institute of Astrophysics of Andalusia. “Observing its atmosphere more closely could allow us to outline an evolutionary path for this planet.”
How such a planet took shape remains a mystery. Scientists hope that new observatories like the James Webb Space Telescope (JWST) can provide answers. By studying its expanded atmosphere, they may reveal something about its past that helps better understand its origin.
A journey of discovery
WASP-193b represents a challenge and a great opportunity for astronomers. Understanding its nature could open new perspectives on the formation of planets and the behavior of gas giants. A cosmic mystery whose solution will require further observations and theoretical work, in particular to measure the properties of its atmosphere and compare them with the various theoretical mechanisms that could lead to such an extreme expansion.
Each new discovery reminds us how vast and amazing the universe is. WASP-193b teaches us that there is still much to discover and that the unexpected is always around the corner. The future of astronomy is bright, fluffy and full of surprises.
