The diversity of exoplanets is astonishing. Sometimes even intriguing. Because astrophysicists have a hard time understanding how WASP-193 b was formed. Indeed, no classical model can explain the presence of this gas giant with an extremely low density, similar to that of cotton candy!
In the category of strange planets, here is WASP-193 b. This gas giant, 1.5 times larger than Jupiter, is indeed one of the… super lightweights! With barely a tenth of the mass of our giant, this recently discovered exoplanet ranks as the second lightest planet in the current catalog, just behind Kepler 51 d. With its extremely low density, it falls into the category of “Puffy Jupiters,” while also being an extreme case.
A “cotton candy” planet
The planet has a density of only 0.059 g/cm3. For comparison, Jupiter has a density of 1.3 g/cm3 and Earth, being a rocky planet, has 5.5 g/cm3. Researchers have compared this density to familiar objects, revealing that WASP-193 b has almost the same density as… cotton candy! Hence, it was given the charming nickname “cotton candy planet.”
Located 1,200 light-years from Earth, WASP-193 b orbits at an extremely close distance to its starstar, only 10.1 million kilometers! It completes a revolution around its sunsun in 6.2 Earth days. Enough to make your head spin!
An exoplanet that defies classical formation models
The researchers, presenting their findings in the journal Nature Astronomy, hypothesize that this exoplanet is mainly composed of heliumhelium and hydrogenhydrogen, very light gases. Its “puffy” appearance is believed to result from the radiation emitted by its very close star. The mystery remains of how such a planet could have formed and been maintained.The cohesion. Due to its position, size, and density, WASP-193 b indeed challenges current theories describing planet formation.
Several thousand exoplanets have already been discovered. Among them, exoplanetsexoplanets, hot Jupiters, but also planets with such low density that astronomersastronomers call them super-puffs. Cosmic cotton candies. Planets that do not resemble any in our solar systemsolar system. At least, that’s what researchers thought until today…
Article by Nathalie MayerNathalie Mayer published on December 23, 2019
In 2012, three exoplanets were discovered orbiting a star named Kepler 51. A star located about 2,400 light years awayyears away from our Earth. A star only 500 million years old. But it was not until 2014 that their astonishing characteristic was revealed. An incredible low density that places them in the category of what astronomers call super-puffs.
Some say they are as light as cotton candy. To be sure, researchers at the University of Colorado in Boulder (United States) observed them using the Hubble Space Telescope. They were able to confirm that their density is less than 0.1 gram per cubic centimeter (g/cm3)). For comparison, Earth’s density is around 5.5 g/cm3 and even Saturn’sSaturn’s – the most gaseous planet in our solar system – is almost 0.69 g/cm3.
“A cotton candy the size of Jupiter!”
“A cotton candy the size of Jupiter!” Even the researchers can’t believe it.They wanted to learn more about the composition of their atmosphere. They encountered something opaque at high altitudes.
### Not So Exceptional Exoplanets
After some additional data and computer simulations, astronomers believe that the atmosphere of these amazing exoplanets is mainly composed of hydrogen and helium. These light gases are capable of creating this fluffy appearance. However, the whole might be covered with a thick methane haze, similar to what happens on Titan, which is also surrounded by a mist rich in carbon.
Researchers from the University of Colorado also observed that the exoplanets around Kepler 51 are ejecting large amounts of gas. For the innermost one, tens of billions of tons of materials are being released into space… every second. This could potentially lead them to lose their vaporous appearance in the future.
In the end, these planets could turn out to be what astronomers call mini-Neptunes, a class of very common exoplanets. Jessica Libby-Roberts, a researcher at the University of Colorado, concludes, “We believe that much of the strangeness of Kepler 51’s exoplanets comes from the fact that we are observing them at an early stage of their development, a phase that we rarely have the opportunity to observe.”