Astronomers spot a giant gas planet that is as light as cotton candy

Amazing stuff!

"Astronomers ... have discovered a huge, fluffy oddball of a planet orbiting a distant star in our Milky Way galaxy. ... is a promising key to the mystery of how such giant, super-light planets form. ...

The new planet, named WASP-193b, appears to dwarf Jupiter in size, yet it is a fraction of its density. The scientists found that the gas giant is 50 percent bigger than Jupiter, and about a tenth as dense — an extremely low density, comparable to that of cotton candy. ..."

From the abstract:

"Gas giants transiting bright nearby stars provide crucial insights into planetary system formation and evolution mechanisms. Most of these planets show certain average characteristics, serving as benchmarks for our understanding of planetary systems. However, outliers like the planet we present in this study, WASP-193 b, offer unique opportunities to explore unconventional formation and evolution processes. This planet completes an orbit around its V-band-magnitude 12.2 F9 main-sequence host star every 6.25 days. Our analyses found that WASP-193 b has a mass of 0.139 ± 0.029 MJ and a radius of 1.464 ± 0.058 RJ, translating into an extremely low density of 0.059 ± 0.014g cm−3, at least one order of magnitude less than standard gas giants like Jupiter. Typical gas giants such as Jupiter have densities that range between 0.2 g cm−3 and 2 g cm−3. The combination of its large transit depth (1.4%), extremely low density, high-equilibrium temperature (1,254 ± 31 K) and the infrared brightness of its host star (K-band magnitude 10.7) makes WASP-193 b an exquisite target for characterization by transmission spectroscopy (transmission spectroscopy metric ~600). One single JWST transit observation would yield detailed insights into its atmospheric properties and planetary mass, providing a unique window to explore the mechanisms behind its exceptionally low density and shed light on giant planets’ diverse nature."

Astronomers spot a giant planet that is as light as cotton candy | MIT News | Massachusetts Institute of Technology The new world is the second-lightest planet discovered to date.

WASP-193 b

An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b (no public access)

WASP-193 b is a gas giant exoplanet that orbits an F-type star. Its mass is 0.139 Jupiters, it takes 6.2 days to complete one orbit of its star, and is 0.0676 AU from its star. Its discovery was announced in 2023.