# Astronomers Discover Two "Super-Puff" Exoplanets Lighter Than Cotton Candy — the Least Dense Gas Giants Ever Found

*2026-06-25 22:02 UTC · Science · 2 min read*

> NASA's TESS mission found TOI-791 b and c — two Jupiter-sized gas giants 35 times less dense than Jupiter and lighter than cotton candy, orbiting a star 1,110 light-years away.

Astronomers have discovered two giant planets so extraordinarily light they are less dense than cotton candy, making them the puffiest worlds ever confirmed. The pair — named TOI-791 b and TOI-791 c — orbit a Sun-like star some 1,110 light-years away in the southern constellation Volans. TOI-791 b is nearly the size of Jupiter but contains just 3% of its mass; TOI-791 c is even larger than Jupiter yet holds only 6% of its mass. Their densities — 0.038 and 0.047 grams per cubic centimeter — are roughly 35 times lower than Jupiter's.

"These two planets have densities comparable to a nice blob of shaving foam, fresh from the can," said George Dransfield of the University of Oxford. Finding two such rare super-puffs orbiting the same star is exceptionally uncommon: fewer than 40 of the nearly 6,300 confirmed exoplanets fall into this category. NASA's TESS satellite gathered 1,122 days of data over seven years to detect the planets through repeated dimming of their host star, and ground-based telescopes pinned down their masses and densities.

The planets are probably composed mostly of hydrogen and helium and may appear white or blue depending on cloud cover. NASA's James Webb Space Telescope is expected to follow up to confirm their chemical makeup. Researchers say the gravitationally linked pair pose a fascinating challenge: "a puzzle for us to solve about how giant planets like Jupiter and the super-puffs form," according to NASA scientist Jon Jenkins. The findings were published in the Monthly Notices of the Royal Astronomical Society.

## Sources

- [science.nasa.gov](https://science.nasa.gov/missions/tess/nasas-tess-mission-reveals-the-puffiest-planets-ever-found/)
- [abcnews.com](https://abcnews.com/Technology/wireStory/astronomers-find-biggest-super-puff-planets-lighter-cotton-134190295)

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TechTools News · https://techtools.cz/tools/news/article/1891-astronomers-discover-two-super-puff-exoplanets-lighter-than-cotton-candy-the
Česká verze: https://techtools.cz/tools/news/clanek/1964-astronomove-objevili-dve-super-nadychane-exoplanety-lehci-nez-cukrova-vata