Massive cloud-like planet as fluffy as cotton candy discovered: ScienceAlert

The galaxy can throw weird curveballs, but an exoplanet discovered 1,232 light-years away is one of the weirdest yet.

It is WASP-193b, and although it is nearly 50% larger than Jupiter, it is so light and fluffy that its overall density is comparable to that of cotton candy. That’s just a hair over 1% of Earth’s density. It’s an absolute dandelion ball of a world… if a dandelion ball could be a planet.

While not unknownexoplanets like WASP-193b are rare, and they could help us better understand planetary evolutionaccording to an international team led by the astronomer Khalid Barkaoui from the University of Liège in Belgium.

A paper describing the discovery has been accepted for publication and is available at arXiv preprint server.

Artist’s impression of a puffy world. (NASA, ESA, CSA, J. Olmsted/STScI)

Looking at all the weird and wonderful worlds out there not only allows us to contextualize our solar system but offers a window into how planetary systems form and evolve.

Gas giants close to their stars are a great tool for this because our understanding of planetary formation means they must have formed elsewhere and migrated inwards. Moreover, the irradiation of the star also means as much of these worlds decrease.

WASP-193b is an exoplanet orbiting a Sun-like star named WASP-193. This star has about 1.1 times the mass and 1.2 times the radius of the Sun and is very close to the Sun in temperature and age. But WASP-193b orbits its star much closer than any planet in the solar system: it zooms in once every 6.25 days.

Studying how the light from the star changes as the exoplanet orbits around it allowed Barkaoui and his colleagues to calculate the Ray And mass. Its radius is about 1.46 times the radius of Jupiter. But its mass is incredibly small by comparison: just 0.139 times that of Jupiter.

From these properties, the researchers deduced the density of the exoplanet: 0.059 grams per cubic centimeter. In comparison, the Earth has a density of 5.51 grams per cubic centimeter. The density of Jupiter is 1.33 grams per cubic centimeter, which makes sense – there are a lot of clouds. Cotton candy has a density of 0.05 grams per cubic centimeter.

Animation showing how radial velocity is measured, one of the ways a planet can affect the light from its star. (Alysa Obertas/Wikimedia Commons/CC BY-SA 4.0)

Very few other worlds have been found with comparable density, but they offer some clues as to how such fluffy worlds may exist. The proximity of a star can heat the atmosphere, inflate it, especially if this atmosphere was mainly hydrogen and helium.

But such a world would only look like WASP-193b for a few tens of millions of years or so, when the star is younger and hotter; moreover, the star’s heat and winds could strip such a tenuous atmosphere quite quickly.

So that poses some problems. The star is thought to be up to 6 billion years old; Although there may be a mechanism for internal heat to inflate WASP-193b’s atmosphere, the observed properties of the exoplanet cannot be recreated using sophisticated models of planetary evolution.

The good news is that WASP-193b represents an excellent candidate for follow-up studies to see what its atmosphere is made of. This is one of the tasks The James Webb Space Telescope was designed For; just one transit observationsays the team, could yield information that explains how such a weird, fluffy world can exist in the Universe.

The team’s research has been accepted for publication and is available at arXiv.

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