Science

Researchers discover planet with density resembling cotton candy

The recently found world ranks as the second-lightest planet ever discovered.

First discovered by the Wide-Angle Search for Planets (WASP), an international collaboration using robotic observatories to monitor the brightness of thousands of stars, WASP-193— situated some 1200 light years away— has been the oddest exoplanet discovered yet. It cannot be explained by current planetary formation theories, making it a true curveball in the face of what we think we know.

Cotton-candy 50% bigger than Jupiter

It’s a planet nearly 50 percent bigger than Jupiter, and it’s so light that Julien de Wit, a professor at MIT and co-author of the study, described the planet as “super fluffy.” These properties hail it’s density comparable to that of cotton-candy, something that could rival a cotton ball or dandelions wrapped into each other to resemble a ball if the entire thing was to then become a planet. 

Astronomer Khalid Barkaoui of University of Liège in Belgium explains that it is the second least dense planet discovered to date, after Kepler 51d which is very significantly smaller.

Cotton-candy
Image from IndiaToday

“Its extremely low density makes it a real 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,” Barkaoui says. 

This discovery can help further research in planetary evolution, not just in understanding similar prototypes but also in understanding our own Solar System. 

WASP-193b is an exoplanet that orbits WASP-193,  a sun-like star. This star, if compared to the Sun, has around 1.1 times the mass and 1.2 times the radius but it is very close to the Sun in temperature and age. However, WASP-193b’s orbit to it’s sun is much more closer than any other planet in our Solar System. It completes an orbit every 6.25 days. 

In between 2006 and 2008 and 2011 and 2012, WASP-South observatory detected periodic dips in light from the star WASP-193. This is how planets are found, by locating a Sun-like star and observing the path of it’s light. If a light dips in regular and equal intervals, it means something is orbiting the star— hence a planet. These intervals were every 6.25 days, in WASP-193b’s case, and the amount of light the planet blocked with each transit gave scientists an estimate of the planet’s size. 

TRAPPIST-South and SPECULOOS-South observatories were then used to measure the planetary signal in different wavelengths and to verify the planetary nature of the eclipsing object. Spectroscopic observations collected by the HARPS and CORALIE spectrographs, in Chile, were used to measure the mass of the planet. These measurements revealed the planet to be of very low density. Its mass and size seemed to be 0.14 and 1.5 that of Jupiter respectively and hence the resulting density came out to be about 0.059 grams per cubic centimetre. Jupiter’s density, for a comparison, is about 1.33 grams per cubic centimetre and Earth is 5.51 grams per cubic centimetre. 

cotton-candy
Image from Sciencealert

Researchers suspect that the new planet is constituted mainly from hydrogen and helium, like other gas giants in the galaxy. These gases, on WASP-193b form an extremely inflated atmosphere that extends tens of thousands of kilometre’s farther than Jupiter’s atmosphere. No existing theory can explain this phenomenon, yet. 

“WASP-193b is a cosmic mystery. Solving it will require some more observational and theoretical work, notably to measure its atmospheric properties with the JWST space telescope and to confront them to different theoretical mechanisms that possibly result in such an extreme inflation,” Barkaoui says.

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