The planet WASP-193b is 50% larger than Jupiter and has a cotton candy-like density. Astronomers have found a planet in the middle of a distant star. The discovery, reported on May 14 in the journal Nature Astronomy, is a promising key to the mystery of how giant, super-light planets form. The planet WASP-193b is a fraction of Jupiter's density and appears to dwarf it in size. The scientists found that the gas giant is about a tenth as dense as cotton candy and 50 percent bigger. WASP-193b is the second lightest planet discovered to date. WASP-193b is an outlier among the more than 5,400 planets discovered to date. Khalid Barkaoui is the lead study author and an MIT PhD candidate. There is a class of planets called puffy Jupiters, and they have been a mystery for fifteen years.
We don't know where to put this planet in all the formation theories we have right now, because it's an outlier. Classical evolution models can't explain how this planet was formed.
The co-authors of the study are an assistant professor in MIT's Department of Earth, Atmospheric and Planetary Sciences, and a MIT graduate student, Artem Burdanov.
WASP is an international collaboration of academic institutions that together operate two robotic observatories, one in the north and the other in the south. Each observatory uses wide-angle cameras to measure the brightness of thousands of individual stars. The WASP-South observatory detected dips in light from WASP-193 in surveys taken between 2006 and 2008 and again in 2011. Astronomers determined that the star's periodic dips in brightness were consistent with a planet blocking the star's light. The scientists estimated the size of the planet with the amount of light that was blocked by transits. The astronomer looked at the mass of the planet to see if it was related to the composition of the planet. Calculating a mass estimate is done by using a technique called radial velocity, in which scientists analyze a star's spectrum of light as a planet circles it. A star's spectrum can be changed in a number of ways depending on what is pulling on it. The closer a planet is to its star, the more the spectrum can shift, which can give scientists an idea of its mass. Calculating the mass of WASP-193 b was accomplished by using additional high-resolution spectrum of the star taken by various ground-based telescopes. They kept coming up empty because the planet was too light to have any pull on its star. De Wit explains that big planets lead to a big pull on their star and are easy to detect. Even though it is big, huge and has low density, it was difficult to detect with just the radial velocity technique.
It took four years to gather data and show that there is a mass signal, but it is really small. We were initially getting low densities, which were very difficult to believe, because this was a very rare occurrence.
An Inflated World.
The team found that the planet was very light, with a mass of 0.14 that of Jupiter. The new, puffy planet has a density of about 0.05 grams per cubic centimeter. The planet is so light that it is hard to think of a solid state material like cotton candy. The planet is very fluffy.
The new planet is thought to be made of hydrogen and helium, similar to other gas giants in the universe. There is no existing theory of planetary formation that can answer the question of how a planet can inflate. The team plans to use a technique de Wit developed to get a better picture of the new fluffy world. The team sees WASP-193b as an ideal candidate for follow-up studies because of its characteristic characteristics. The planet is one of the best targets for studying atmospheric effects. It will be a stone to try and solve the mystery of Jupiters.
Khalid Barkaoui, Francisco J. Pozuelos, Coel Hellier, Barry Smalley, Louise D. R. Anderson, Francois Bouchy, Artem Burdanov, Laetitia Delrez and Pierre F. L. Maxted were present. There is a DOI: 10.1038/s41550-024-02259-y
The research was funded by the UK's Science and Technology Facilities Council for WASP, the European Research Council, the Wallonia-Brussels Federation, and the Heising-Simons Foundation.