A global staff led by researchers from the EXOTIC Laboratory of the College of Liège, in collaboration with MIT and the Astrophysics Institute in Andalusia, has simply found WASP-193b, a very low-density big planet orbiting a distant Solar-like star.

This new planet, positioned 1,200 light-years from Earth, is 50% bigger than Jupiter however seven occasions much less large, giving it a particularly low density corresponding to that of cotton sweet. “WASP-193b is the second least dense planet found to this point, after Kepler-51d, which is way smaller,” explains Khalid Barkaoui, a Postdcotral Researcher at ULiège’s EXOTIC Laboratory and first writer of the article printed in Nature Astronomy. Its extraordinarily low density makes it an actual anomaly among the many greater than 5 thousand exoplanets found to this point. This extremely-low-density can’t be reproduced by normal fashions of irradiated fuel giants, even beneath the unrealistic assumption of a coreless construction.”

The brand new planet was initially noticed by the Vast Angle Seek for Planets (WASP), a world collaboration of educational establishments that collectively operated two robotic observatories, one within the northern hemisphere and the opposite within the south. Every observatory used an array of wide-angle cameras to measure the brightness of hundreds of particular person stars throughout all the sky. In information taken between 2006 and 2008, and once more from 2011 to 2012, the WASP-South observatory detected periodic transits, or dips in gentle, from the star WASP-193. Astronomers decided that the star’s periodic dips in brightness have been according to a planet passing in entrance of the star each 6.25 days. The scientists measured the quantity of sunshine the planet blocked with every transit, which gave them an estimate of the planet’s dimension.

The staff used then the TRAPPIST-South and SPECULOOS-South observatories — directed by Michaël Gillon, FNRS Analysis Director and astrophysicist at ULiège — positioned within the Atacama Desert in Chile to measure the planetary sign in several wavelengths and to validate the planetary nature of the eclipsing object. Lastly, additionally they used spectroscopic observations collected by the HARPS and CORALIE spectrographs — additionally positioned in Chile (ESO)- to measure the mass of the planet. To their nice shock, the collected measurements revealed a particularly low density for the planet. Its mass and its dimension, they calculated, have been about 0.14 and 1.5 that of Jupiter, respectively. The ensuing density got here out to about 0.059 grams per cubic centimeter. Jupiter’s density, in distinction, is about 1.33 grams per cubic centimeter; and Earth is a extra substantial 5.51 grams per cubic centimeter. One of many supplies closest in density to the brand new, puffy planet, is cotton sweet, which has a density of about 0.05 grams per cubic centimeter.

“The planet is so gentle that it is troublesome to consider a similar, solid-state materials,” says Julien de Wit, professor at Massachusetts Institute of Expertise (MIT) and co-author. “The rationale why it is near cotton sweet is as a result of each are just about air. The planet is principally tremendous fluffy.”

The researchers suspect that the brand new planet is made largely from hydrogen and helium, like most different fuel giants within the galaxy. For WASP-193b, these gases doubtless kind a massively inflated ambiance that extends tens of hundreds of kilometers farther than Jupiter’s personal ambiance. Precisely how a planet can inflate a lot is a query that no present concept of planetary formation can but reply. It definitely requires a big deposit of power deep into the planet’s inside, however the particulars of the mechanism are usually not but understood. “We do not know the place to place this planet in all of the formation theories now we have proper now, as a result of it is an outlier of all of them. We can’t clarify how this planet was fashioned. Trying extra carefully at its ambiance will permit us to constrain an evolutionary path of this planet, provides Francisco Pozuelos, astronomer on the Instituto de Astrofisica de Andalucia (IAA-CSIC, Granada, Spain).”

“WASP-193b is a cosmic thriller. Fixing it is going to require some extra observational and theoretical work, notably to measure its atmospheric properties with the JWST area telescope and to confront them to completely different theoretical mechanisms that presumably lead to such an excessive inflation”, concludes Khalid Barkaoui.


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