Super Fluffy “Cotton Candy” Exoplanet Discovery Stuns Scientists – “We Can’t Tell How This Planet Formed”

Astronomers have discovered a giant, low-density planet called WASP-193b, which is 50% larger than Jupiter but has the density of cotton candy. This discovery challenges existing planet formation theories. (Artist’s concept.) Credit:

Astronomers have discovered a giant, low-density planet called WASP-193b, which is 50% larger than Jupiter But its density is like cotton candy. This discovery challenges current planet formation theories, as scientists cannot explain how such a planet could form.

Astronomers have discovered a giant, fluffy strange sphere orbiting a distant star from our planet Galaxy Galaxy. The discovery, reported May 14 in the journal nature astronomy by researchers from withAt the University of Liège in Belgium and elsewhere, there is a promising key to the mystery of how such massive, super-light planets form.

The new planet, named WASP-193b, appears to be smaller in size than Jupiter, yet at a fraction of its density. Scientists found that the gas giant is 50 percent larger than Jupiter, and about one-tenth as dense – extremely less dense than cotton candy.

WASP-193b is the second lightest planet ever discovered, after a minor planet. Neptune-Like world, Kepler 51d. The enormous size of the new planet, combined with its super-light density, makes WASP-193b one of the strangest planets among the more than 5,400 discovered so far.

“It’s really rare to find these massive objects with such low density,” says lead study author and MIT postdoc Khaled Barkaoui. “There is a class of planets called puffy Jupiters, and it has been a mystery for 15 years what they are. And this is an extreme case of that category.

“We don’t know where to place this planet in all the formation theories that we have at the moment, because it is different from all of them,” says co-lead author Francisco Pozuelos, a senior researcher at the Institute of Astrophysics of Andalusia. In Spain. “Based on the classical evolution model we cannot tell how this planet formed. Looking more closely at its atmosphere will help us get a better idea of ​​the planet’s evolutionary path.

MIT co-authors of the study include Julian de Wit, assistant professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences, and MIT postdoc Artem Burdanov, as well as colleagues from several institutions across Europe.

WASP-193b system

Artist’s impression of the WASP-193b system. Credit: University of Liège

“An interesting twist”

The new planet was initially observed by the Wide Angle Search for Planets, or WASP – an international collaboration of academic institutions that simultaneously operates two robotic observatories, one in the Northern Hemisphere and the other in the South. Each observatory uses an array of wide-angle cameras to measure the brightness of thousands of individual stars across the sky.

In surveys conducted between 2006 and 2008 and again between 2011 and 2012, the WASP-South Observatory detected periodic transits, or dips in light, from WASP-193 – a bright, nearby star located 1,232 light years from Earth. Ka, a sun-like star. Astronomers determined that the periodic dips in the star’s brightness were consistent with a planet orbiting the star and blocking its light every 6.25 days. Scientists measured the total amount of light blocked by the planet during each transit, giving them an estimate of the planet’s huge, super-Jupiter size.

Astronomers then tried to deduce the planet’s mass – a measure that would reveal its density and potentially also give clues to its composition. To get an estimate of the mass, astronomers typically use radial velocity, a technique in which scientists analyze a star’s spectrum, or different wavelengths of light, as a planet orbits the star. The spectrum of a star can be shifted in specific ways depending on whatever is pulling on the star, such as an orbiting planet. The more massive a planet is, and the closer it is to its star, the more its spectrum can shift – a distortion that can give scientists an idea of ​​the planet’s mass.

For WASP-193 b, astronomers obtained additional high-resolution spectra of the star taken by various ground-based telescopes, and attempted to employ radial velocity to calculate the planet’s mass. But they kept coming up empty – precisely because, as it turned out, the planet was so light that there was no detectable tug on its star.

“Generally, larger planets are much easier to detect because they are generally more massive, and exert a larger drag on their star,” De Wit explains. “But what was intriguing about this planet was that even though it is big – huge – its mass and density are so low that it was really very difficult to detect with just radial velocity techniques. This was an interesting twist.”

,[WASP-193b] It is so faint that it took four years to collect data and show that there is a massive signal, but it is actually very small,” Barkaoui says.

“We were finding extremely low density, which was very hard to believe at first,” says Pozuelos. “We repeated the process of analyzing all the data several times to make sure that this was the actual density of the planet because it was extremely rare.”

a swollen world

Ultimately, the team confirmed that the planet was indeed extremely light. They calculated that its mass was about 0.14 that of Jupiter. And its density derived from its mass came out to be approximately 0.059 grams per cubic centimeter. In contrast, Jupiter has about 1.33 grams per cubic centimeter; And Earth is more significant 5.51 grams per cubic centimeter. Perhaps the material closest in density to the new, swollen planet is cotton candy, which has a density of about 0.05 grams per cubic centimeter.

“The planet is so light that it’s difficult to think of a consistent, solid-state substance on it,” Barkaoui says. “The reason it is closer to cotton candy is that both are composed mostly of light gases rather than solids. The planet is basically super hairy.”

Researchers suspect that the new planet is composed mostly of hydrogen and helium, like most other gas giants in the galaxy. For WASP-193b, these gases likely create a highly inflated atmosphere that extends thousands of kilometers farther than Jupiter’s own atmosphere. How a planet can swell so far while maintaining super-light density is a question that no existing theory of planet formation has yet been able to answer.

To get a better picture of the new fuzzy world, the team plans to use previously developed De Wit technology to first obtain some properties of the planet’s atmosphere, such as its temperature, composition and pressure at different depths. . These characteristics can then be used to accurately determine the planet’s mass. For now, the team sees WASP-193b as an ideal candidate for follow-up studies with observatories such as James Webb Space Telescope,

“The larger a planet’s atmosphere, the more light can penetrate,” De Wit says. “So it’s clear that this planet is one of the best targets we have for studying atmospheric effects. It will be a Rosetta Stone for trying to solve the mystery of swollen Jupiter.

Reference: “An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b” Khaled Barkaoui, Francisco J. By Pozuelos, Koel Hellier, Barry Smalley, Lewis D. Nielsen, Prajwal Niraula, Michael Gillon, Julian De Wit. Simon Muller, Caroline Dorn, Revit Held, Emmanuel Jehin, Brice-Olivier Demory, Valérie Van Grootel, Abderrahmane Soubakiu, Mourad Ghachaoui, David. R. Anderson, Zouhair Benkhaldoun, Francois Bouchy, Artem Burdanov, Letitia Delraz, Elsa Ducrot, Lionel Garcia, Abdelhadi Jabiri, Monica Lendl, Pierre FL Maxted, Catriona A. Murray, Peter Pihlmann Pedersen, Didier Queloz, Daniel Sebastian, Oliver Turner, Stephan Udry, Mathilde Timmermans, Amaury HMJ Triad, and Richard G. West, May 14, nature astronomy,
DOI: 10.1038/s41550-024-02259-y

This research was funded, in part, by the UK Science and Technology Facility Council for Consortium Universities and WASP; European Research Council; Wallonia-Brussels Federation; and the Heising-Simons Foundation, Colin and Leslie Mason, and Peter A. Gilman, Artemis and others are supporting the Speculoos telescope.


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