NASA’s Transiting Exoplanet Survey Satellite, launched in 2018, has uncovered the two puffiest planets yet seen: TOI-791 b and TOI-791 c. Both match Jupiter’s size, yet their masses are only 3 % and 5.9 % of its, giving them densities comparable to cotton candy. The pair orbit a single star in a rare configuration.

Lead researcher George Dansfield of Oxford University noted that only a handful of super‑puffy worlds are known, making this dual discovery especially uncommon. TESS gathered 1,122 days of data over seven years, revealing the planets’ extended orbits and mutual gravitational tug that skews their transit timing.

NASA Ames scientist Steve Howell highlighted the value of studying such low‑mass, giant‑size planets, arguing they illuminate giant‑planet formation theories. Understanding their atmospheric composition and rotational dynamics could explain how “cotton candy” worlds assemble in the first place.

With 7,931 exoplanet candidates already catalogued, these findings reinforce TESS’s role in mapping nearby worlds. The discovery underscores the diversity of planetary systems and the need for continued observation to unravel the mechanisms behind these inflated gas giants. Their unexpected mass deficits challenge conventional models of core accretion and atmospheric retention.