Mysteries of WASP-193b, an exoplanet that looks like cotton candy and intrigues scientists

Features of WASP-193b explain why this exoplanet is intriguing to both astronomy buffs and space science experts. Let’s start with the fact that, given its characteristics, it is located outside the Solar System. In addition, it is a true giant in space: it is 50% larger than the gas giant Jupiter. On the other hand, you need to pay attention to its composition. Due to its low density, experts compare it to cotton candy. or with a bouncy castle.

To unravel the mysteries of this exoplanet, an international team of researchers proposes an approach in a study recently published in Nature Astronomy. As the astronomers explain in the report, their object of analysis is the second least dense planet known to date. In this regard, it is ahead only of Kepler-51d, which, by the way, is much smaller.

Because Very low-density exoplanets continue to intrigue both fans and connoisseurs? What processes explain this uniqueness of its composition? Are they really comparable to cotton? That is, if we touched them, would we feel a texture similar to that of a sponge? To answer these and other questions, Hypertext spoke exclusively with Francisco Pozuelos (41), astronomer at the Institute of Astrophysics of Andalusia and co-author of the new study.

WASP-193b: 10 facts about the exoplanet that are compared to cotton candy

• It was discovered as recently as 2023, according to NASA.
• The US Space Agency describes it as “giant made mostly of gases“
• Found in the group of exoplanets. At the moment, about 5,500 such objects have been discovered outside the solar system.
• It is located approximately 1200 light years from Earth.
• Its size 50% more compared to Jupiter, which is the largest planet in the solar system. The coefficient is 1.5.
• On the other hand, its mass is 0.14 compared to Jupiter. This results in a sevenfold reduction in density.
• Read more about its density. It is indicated to be 0.059 grams per cubic centimeter. For comparison, cotton candy is about 0.05 grams per cubic centimeter. In turn, for our planet it is 5.51 grams per cubic centimeter.
• “WASP-193b is so light that it is difficult to imagine a similar material in a solid state.“Julien de Wit, one of the authors of the study and a scientist at the Massachusetts Institute of Technology (MIT), commented on this statement. “The reason it looks like cotton candy is because they’re both almost fluffy. “The planet is essentially very spongy,” he described.
• The team, which also includes Spaniards Pozuelos, believes that the exoplanet consists mainly of hydrogen and helium.
• As we can see in this interactive graph, the system comes with WASP-193, an F-type star. This classification combines stellar variants whose mass is 1–1.4 times the mass of the Sun. In this case, the exoplanet takes just over six days to complete its orbit.

“The existence of plans like WASP-193 raises new questions and opportunities,” Pozuelos says.

“WASP-193b is primarily air. But we must remember that air consists of elements. In the case of the Earth – nitrogen, oxygen, carbon dioxide, neon and helium – and others, but in smaller quantities. In the case of this exoplanet, we believe that The lighter elements, hydrogen and helium, predominate, which explains the relaxed atmosphere.“, Pozuelos explains in dialogue with Hypertext. Based in Granada, he is currently a member of the Exoplanets and Low Mass Stars Research Group of the Institute of Astrophysics of Andalusia (IAA-CSIC).

-How and when did your interest in this exoplanet begin?

– In 2019, my colleague Khalid Barkaoui, at that time a graduate student at the University of Liege in Belgium (I was a postdoctoral fellow at the same university), came to my office. He asked me some technical questions about the WASP project we were involved in. We spent the whole morning checking different stars and one of them saw clear signs that there was something interesting here. I suggested making a few analysis to make sure it was a planet and not something else, such as a double star, what we call a false positive.

A couple of days later he returned to my office to show me his preliminary results. This already indicated that this was no ordinary planet. We presented our discovery to the rest of the research team and started up all the equipment. Observations using more telescopes, racial velocity measurements, statistical analysis, etc.

-What does its very low density mean? How appropriate is the comparison to cotton candy?

– WASP-193b’s low density suggests it likely has a huge atmosphere, much larger than that of our Jupiter. This pomposity, in turn, must hide the mystery of how the planet formed and evolved to its current state. The comparison to cotton candy is just to give us a visual idea of ​​how light it is.. Their density is very similar, but of course it is not sweet or pink.

-How was WASP-193b discovered? More broadly, how do we determine the characteristics of a planet outside the solar system?

– Initially, the planet was discovered by the transit method, which is based on monitor the brightness of the star, waiting for it to decrease. That is, the darkening of the star is produced by an opaque object (planet) that is located between the observer and the star. And this should be done periodically.

Using this method, we determined the size of WASP-193b to be 50% larger than Jupiter (~1.5Rj). To measure its mass, we use the radial velocity method, which is based on the Doppler effect – the same thing that causes ambulances to sound different when they are moving away from us than when they are approaching us. In the case of stars, this effect occurs because the planet is not actually orbiting the star, but the star-planet system is orbiting the center of mass. Although this center of mass is located very close to the star, it causes it to move slightly, a kind of wobble, moving closer and further from us with the same period as the planet orbiting it, and we can measure this Doppler effect in its light.

Using this method we determine that WASP-193b’s mass is only one-seventh that of Jupiter. (~0.14MJ). Combining the size and mass obtained by observations, all that remains is to calculate and find the average density of the object, which in this case turned out to be 25 times less than the density of Jupiter, ~0.059 g/cm3. This roughly corresponds to the density of cotton candy (0.05 g/cm3).

– What are the main mysteries surrounding WASP-193b?

– We know that it is made of air. But the fact is that if the atmosphere consists of these very light elements, and given the age of the star-planet system, it should already have been lost due to the action of stellar radiation. However, here it is. How is this possible? We don’t know yet.

This type of planet with a density below 0.1 g/cm3 is a subcategory of what we call plump Jupiters. We know about ten objects of this type out of a total of more than 5,500 exoplanets discovered today. That is, these ultra-light planets are very rare. But the whole point is that we do not fully understand how they are formed; they have remained a mystery for more than 15 years. Current models of planet formation cannot explain them, which tells us that there must be some unknown physical mechanism that allows this to happen.

– What’s next in the investigation? What are the next steps to take to learn more about this WASP-193b?

– The next step will be a detailed study of its atmosphere. Knowing what chemical elements it consists of and in what quantities they are distributed will give us information about how the planet was formed and what its evolution was like. So we can begin to find out what is this mechanism that we don’t know about that makes these planets exist.

The best tool for this is James Webb. In the next cycle of observations of this space telescope, we will try to find time to accurately carry out all these analyzes. Getting time at James Webb is never easy, you need to prepare a well-reasoned and convincing observation proposal in order to be allowed to use it. But we think we have a scientific case that deserves it, although it will have to wait.

Finally, if we knew more details about WASP-193b, what information would it tell us beyond the exoplanet itself, about the universe more broadly?

– It is recognized that our current models explaining planet formation are incomplete because they do not take into account certain categories of planets, including ultra-light ones. This recognition stimulates our constant search Better understanding of the formation of planetary systems, which ultimately reflects the search for self-knowledge. We wonder what our place is in the galaxy and universe, whether our solar system and Earth are simply the result of frequent and established processes suggesting the possibility of life on other planets, or whether we are the result of chaotic events and a rarity that would leave us alone in a vast Universe.

“The existence of planets like WASP-193b not only challenges our current models, but also raises new questions and possibilities.”reminding us that there are still many mysteries in the universe to be explored, and that each discovery brings us closer to understanding our place in the cosmos,” concludes Pozuelos.