Scientists Discover Record-Breaking “Super-Puff” Planets Lighter Than Cotton Candy

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Astronomers have identified the largest super-puff planets yet discovered, with densities so low they are described as lighter than cotton candy, according to a study published in Science on June 25, 2026. The findings, led by a team including George Dransfield, a planetary astrophysicist at the University of Cambridge, mark a significant advancement in understanding planetary formation and the diversity of exoplanets.

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What are super-puff planets?
Super-puff planets are a class of exoplanets characterized by their unusually low density, with atmospheres that expand to enormous sizes relative to their mass. These planets often orbit close to their host stars, leading to extreme atmospheric conditions. The newly discovered planets, named TOI-1772 b and TOI-1772 c, are part of a system approximately 1,200 light-years away in the constellation Lyra. Their densities are comparable to that of a marshmallow, with TOI-1772 b having a radius 12 times that of Earth but a mass only 3.5 times Earth’s.

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How were they discovered?
The discovery relied on data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which detects planetary transits by measuring dips in starlight. Follow-up observations using the European Space Agency’s (ESA) CHEOPS satellite and ground-based telescopes in Chile and Hawaii confirmed the planets’ existence. Researchers analyzed light curves and radial velocity measurements to determine their size, mass, and atmospheric composition. The team noted that the planets’ low densities suggest they may have retained primordial hydrogen and helium envelopes, a feature rare among exoplanets.

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Why this matters for astronomy
The identification of TOI-1772 b and c challenges existing models of planetary formation. Traditional theories suggest that planets of this size would have accreted heavy elements early in their evolution, but the super-puff configuration implies a different developmental path. “These planets could have formed farther from their star, where icy materials were abundant, and then migrated inward,” Dransfield said in a statement. The findings also highlight the role of stellar radiation in stripping away planetary atmospheres, a process that could explain why some super-puff planets exist in close orbits.

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Comparisons to prior discoveries
This discovery builds on the 2023 detection of K2-290 b, another super-puff planet with a density similar to a sponge. However, TOI-1772 b is nearly twice as large as K2-290 b, making it the most extreme example yet. Researchers at the Harvard-Smithsonian Center for Astrophysics noted that the new findings could help refine estimates of how many such planets exist in the Milky Way. “If super-puff planets are common, it suggests that planetary systems are more diverse than previously thought,” said Dr. Sarah Ballard, an exoplanet researcher not involved in the study.

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What’s next for the research?
The team plans to use the James Webb Space Telescope (JWST) to study the atmospheric composition of TOI-1772 b and c in greater detail. Initial data from JWST’s mid-infrared instruments could reveal whether the planets have detectable methane or water vapor, which would provide clues about their origins. Additionally, the European Extremely Large Telescope (E-ELT), scheduled to begin operations in 2027, may offer higher-resolution observations of similar exoplanets.

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Implications for future missions
The discovery underscores the importance of missions like TESS and CHEOPS in expanding the exoplanet catalog. NASA’s upcoming Nancy Grace Roman Space Telescope, set for launch in 2027, is expected to detect even more super-puff planets by surveying a broader area of the sky. Astronomers hope that continued observations will clarify whether these planets are a transient phase in planetary evolution or a stable class of objects.

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Expert reactions
The findings have drawn praise from the scientific community. Dr. Nikku Madhusudhan of the University of Cambridge, who studies exoplanet atmospheres, called the discovery “a critical data point for understanding how planetary systems form and evolve.” Meanwhile, some researchers caution against overgeneralizing from a single system. “While TOI-1772 is an exceptional case, we need more examples to determine if super-puff planets are a common phenomenon,” said Dr. Laura Kreidberg of the Max Planck Institute for Astronomy.

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Conclusion
The identification of the largest super-puff planets yet observed represents a milestone in exoplanet research. By combining data from multiple observatories, astronomers have uncovered a new frontier in planetary science, raising questions about the mechanisms that shape planetary systems. As new telescopes come online, the study of these ethereal worlds is poised to reveal even more about the universe’s cosmic diversity.