How can this exoplanet as dense as cotton candy exist?

How can this exoplanet as dense as cotton candy exist?
How can this exoplanet as dense as cotton candy exist?

In the category of strange planets, here is WASP-193 b. This gas giant 1.5 times larger than JupiterJupiter is indeed one of the… super featherweights! With barely a tenth of the mass of our giant, this recently discovered exoplanet ranks second among the “lightest” planets in the current catalog, just behind Kepler 51 d. With its extremely low density, it thus enters the class of “swollen Jupiters” (puffy Jupiter)while representing an extreme case.

A “cotton candy” planet

The planet actually has a density of only 0.059 g/cm3. For comparison, Jupiter has a density of 1.3 g/cm3 and Earth, which is a rocky planet, 5.5g/cm3. The researchers had fun comparing this density to objects that we know, and it turns out that WASP-193 has approximately the same density… as cotton candy! Which earned him the nice nickname “ cotton candy planet “.

Located 1,200 light years from Earth, WASP-193 b orbits at an excessively short distance from its starstar. Only 10.1 million kilometers! She thus goes around her sunsun in 6.2 Earth days. Enough to make you dizzy!

An exoplanet that defies classic models of planetary formation

The researchers, who present their results in the journal Nature Astronomysuppose that this exoplanet would be composed essentially ofheliumhelium and D’hydrogenhydrogenof the gasgas very light. Its “inflated” appearance would result from the action of radiation emitted by its very close star. It remains to be understood how such a planet was able to develop and maintain its cohesion. By its position, its size and its density, WASP-193 b indeed defies current theories describing the formation of planets.


Several thousand exoplanets have already been discovered. Among them, exoterresexoterresof the Hot JupitersHot Jupitersbut also planets of such low density that the astronomersastronomers call them super-swollen. Cosmic cotton candy. Planets that are unlike any of those in our world Solar systemSolar system. At least that’s what researchers thought until today…

Article from Nathalie MayerNathalie Mayer published on December 23, 2019

In 2012, three exoplanets were discovered orbiting a star called Kepler 51. A star located some 2,400 light yearslight years of our Earth. A star only 500 million years old. But it wasn’t until 2014 that their astonishing feature was brought to light. An incredible low density that puts them in the category of what astronomers call super-bloated exoplanets.

Some say they are as light…as cotton candy. To find out, researchers from the University of Colorado at Boulder (United States) observed them using the Hubble space telescopeHubble space telescope. They were thus able to confirm that their density is less than 0.1 gram per cubic centimeter (g/cm3)). For comparison, know that that of the Earth is around 5.5 g/cm3 and that even that of SaturnSaturn – the most vaporous planet in our Solar System – is almost 0.69 g/cm3.

“Cotton candy the size of Jupiter!”

“A cotton candy the size of Jupiter!” » The researchers themselves can’t believe it. They therefore wanted to know more about the composition of their atmosphereatmosphere. And they ran into a wallwall. Something opaque at altitude.

Not so exceptional exoplanets

Some additional data and some computer simulationscomputer simulations Later, astronomers believe that the atmosphere of these amazing exoplanets is mainly composed of hydrogen and helium. These light gases are quite capable of creating this fluffy appearance. But the whole thing could be covered with a thick hazehaze of methane. A bit like what happens to TitanTitan which is also surrounded by a fogfog rich in carboncarbon.

Another observation by researchers at the University of Colorado: the exoplanets of Kepler 51 eject large quantities of gas. For the most interior of them, tens of billions of tons of materials are released into the void… every second. Enough to possibly, in the future, make them lose their vaporous appearance.

Ultimately, these planets could turn out to be what astronomers call mini-Neptune. A most common class of exoplanets. “We think that much of the strangeness of the Kepler 51 exoplanets comes from the fact that we are observing them at an early point in their development. Phase that we rarely have the opportunity to observe »concludes Jessica Libby-Roberts, researcher at the University of Colorado.

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