Gas giant exoplanets around nearby bright stars provide important insights into the mechanisms of planetary system formation and evolution. Most of these planets exhibit certain average characteristics and serve as benchmarks for understanding planetary systems. However, outliers like WASP-193b provide a unique opportunity to investigate unconventional formation and evolutionary processes. The mass of this exoplanet is 0.14 times the mass of Jupiter, and its radius is 1.5 times the radius of Jupiter, resulting in an extremely low density of 0.059 g/cm.3at least an order of magnitude smaller than standard gas giants like Jupiter.
“WASP-193b is the second least dense planet ever discovered, after the much smaller Kepler-51d,” said Dr. Khalid Barkaoui, an astronomer at the University of Liège.
“Its extremely low density makes it truly an anomaly among the more than 5,000 exoplanets discovered to date.”
“This extremely low density cannot be reproduced by standard models of irradiated gas giant planets, even under the unrealistic assumption of a coreless structure.”
WASP-193b orbits an F9 main sequence star called . WASP-193 Once every 6.25 days.
This system, also known as TIC 49043968, located It is located in the constellation Hydra, 1,200 light years from Earth.
WASP-193b was first detected in archival data. Wide angle search for planets (Wasp).
Dr. Barkaoui and his colleagues then used the TRAPPIST-South and SPECULOOS-South observatories to measure planetary signals at different wavelengths to verify the planetary nature of the eclipsing object.
Finally, they used spectroscopic observations collected by HARPS and the CORALIE spectrometer to measure the planet's mass.
“The measurements revealed that Earth has a very low density. Its mass and size, they calculated, were about 0.14 and 1.5 that of Jupiter, respectively.”
“The resulting density was approximately 0.059 g/cm.”3. In contrast, Jupiter's density is about 1.33 g/cm.3; Earth is even more substantial at 5.51 g/cm.3”
“One of the materials whose density is closest to that of our new fluffy planet is cotton candy, which has a density of about 0.05 g/cm.3”
“Earth is so light that it's difficult to think of similar solid materials,” said MIT professor Julian de Witt.
“They're similar to cotton candy because they're both similar to air. This planet is basically very fluffy.”
Astronomers suggest that WASP-193b, like most other gas giant planets in the Milky Way, is made primarily of hydrogen and helium.
These gases may form a vastly expanded atmosphere that extends tens of thousands of kilometers farther than Jupiter's own atmosphere.
Exactly how a planet can expand so much is a question that cannot yet be answered by existing theories of planet formation.
Indeed, it requires the deposition of large amounts of energy deep into the planet's interior, but the details of the mechanism are still not understood.
“I don't know where to place this planet among all the geological theories that we currently have, because it's an outlier among all the geological theories. I don't know how this planet formed. “We cannot explain why,” said Dr. Francisco Pozuelos, an astronomer at the Andalusian Institute of Astronomy.
“By looking more closely at its atmosphere, we may be able to constrain the planet's evolutionary path.”
“WASP-193b is a cosmic mystery. Solving it will require further observational and theoretical research, especially using Webb to measure the properties of the atmosphere that cause such extreme inflation. “We need to confront the different possible theoretical mechanisms,” Dr. Barkaoui said.
This finding is reported in the following article: paper in diary natural astronomy.
_____
K. Barkawi other. A low-density atmosphere surrounding the Jupiter-sized planet WASP-193b. Nat Astron, published online March 24, 2024. doi: 10.1038/s41550-024-02259-y
Source: www.sci.news
