New giant planet with the density of cotton candy

May 14. () –

An international team of astrophysicists has just discovered WASP-193b, a giant planet of extraordinarily low density that orbits a distant star similar to the Sun.

This new planet, located 1,200 light years from Earth, It is 50% larger than Jupiter but seven times less massive, giving it an extremely low density, comparable to that of cotton candy.

“WASP-193b is the second least dense planet discovered to date, after Kepler-51d, which is much smaller,” explains Khalid Barkaoui, postdoctoral researcher at the EXOTIC Laboratory of the University of Liège and first author of the article published in Nature Astronomy.

“Its very low density makes it a true anomaly among the more than five thousand exoplanets discovered to date. This extremely low density cannot be reproduced by standard models of irradiated gas giants, even under the unrealistic assumption of a coreless structure,” he explained.

The new planet was initially discovered by the Wide Angle Search for Planets (WASP), an international collaboration of academic institutions that together operated two robotic observatories, one in the northern hemisphere and the other in the southern hemisphere. Each observatory used a series of wide-angle cameras to measure the brightness of thousands of individual stars across the sky, Eureka Alert reports.

In data taken between 2006 and 2008, and again between 2011 and 2012, the WASP-South observatory detected periodic transits, or light falls, of the star WASP-193. Astronomers determined that the star’s periodic dips in brightness were consistent with a planet passing in front of the star every 6.25 days. Scientists measured the amount of light the planet blocked during each transit, which gave them an estimate of the size of the planet.

The team then used the TRAPPIST-South and SPECULOOS-South observatories, led by Michaël Gillon, an astrophysicist at the University of Liège, located in the Atacama Desert in Chile, to measure the planetary signal at different wavelengths and validate the nature planetary of the eclipsing object. Finally, they also used spectroscopic observations collected by the HARPS and CORALIE spectrographs – also located in Chile (ESO) – to measure the mass of the planet.

THE PLANET IS BASICALLY SUPER FLOUGH

Much to their surprise, the accumulated measurements revealed an extremely low density for the planet. Its mass and size, they calculated, were approximately 0.14 and 1.5 those of Jupiter, respectively. The resulting density was approximately 0.059 grams per cubic centimeter. Jupiter’s density, by contrast, is about 1.33 grams per cubic centimeter; and the Earth weighs 5.51 grams per cubic centimeter. One of the materials closest in density to the new, swollen planet is cotton candy, which has a density of approximately 0.05 grams per cubic centimeter.

“The planet is so light that it is difficult to think of an analogous material in a solid state,” says Julien de Wit, a professor at the Massachusetts Institute of Technology (MIT) and co-author of the study. “The reason it looks like cotton candy is because they’re both practically air. The planet is basically super fluffy“.

Researchers suspect that the new planet is made primarily of hydrogen and helium, like most other gas giants in the galaxy. For WASP-193b, these gases likely form a massively inflated atmosphere that extends tens of thousands of kilometers beyond Jupiter’s own atmosphere. How exactly a planet can become so inflated is a question. which no existing theory of planetary formation can answer yet.

It certainly requires a significant reservoir of energy deep within the planet’s interior, but the details of the mechanism are not yet understood. “We do not know where to place this planet in all the formation theories that we have now, because it is an atypical case of all of them. We cannot explain how this planet formed. Taking a closer look at its atmosphere will allow us to delimit the evolutionary path of this planet. planet, adds Francisco Pozuelos, astronomer at the Institute of Astrophysics of Andalusia (IAA-CSIC), who participated in the study.