Astronomers have identified a pair of extraordinarily low-density giant planets that challenge conventional understanding of how planetary systems form and evolve, offering new insights into the diversity of worlds beyond our solar system.
The two planets, detected by NASA's Tess satellite and studied by researchers at the University of Oxford, orbit a star 1,110 light-years away in the southern constellation Volans. What makes these worlds remarkable is their extreme lightness: they are larger than Jupiter yet have densities comparable to cotton candy or shaving foam fresh from the can, making them the largest exoplanets ever found with such minimal density.
"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 in describing the findings, which the research team reported Wednesday in Monthly Notices of the Royal Astronomical Society.
Understanding Rare Cosmic Phenomena
Super-puffs—the technical term for these unusually low-density planets—represent a rare category in the cosmos. Of the nearly 6,300 confirmed exoplanets currently catalogued by NASA, fewer than 40 are classified as super-puffs, according to Dransfield. The discovery of this particularly large pair adds crucial data to the limited sample scientists have for studying these anomalous worlds.
The two planets are believed to be composed primarily of hydrogen and helium, though Dransfield noted that follow-up observations by NASA's Webb Space Telescope will be needed to confirm their chemical composition. Visually, the researcher suspects the planets are probably white or blue depending on cloud cover in their atmospheres, though they will not display the pink hues the term "cotton candy" might suggest.
Formation and Evolution Mysteries
Scientists theorize that super-puffs form in regions around newborn stars where gas is abundant relative to dust. According to current models, these planets initially accumulate substantial gaseous atmospheres but then lose much of this material over time through atmospheric stripping, leaving behind the remarkably light worlds observed today.
The research team determined the planets' density by studying their orbital characteristics using Earth-based telescopes, allowing them to make precise measurements across the vast distance of 1,110 light-years—nearly 6 trillion miles (9.7 trillion kilometers).
For context, Jupiter, the largest planet in our own solar system, is as much as 35 times denser than these two lightweight giants, underscoring just how unusual these discoveries are.
Why This Matters:
The discovery of these super-puff planets expands humanity's understanding of planetary diversity and formation processes across the universe. By studying rare and exotic planetary systems, scientists gather empirical data that refines theoretical models of how planets form, migrate, and evolve—knowledge that deepens our comprehension of our own solar system's origins. These findings represent the kind of fundamental scientific inquiry that benefits from sustained public investment in space exploration and astronomical research. As Dransfield noted, "by studying exotic systems containing rare planet types, we add further pieces to the puzzle of planet formation and learn more about our place in the cosmos." This research demonstrates how continued commitment to scientific exploration yields discoveries that expand human knowledge and our understanding of the universe's complexity.