Astronomers have identified two exoplanets so low in density they defy conventional classification. Dubbed "super-puffs," these worlds orbit the same star and possess densities lower than cotton candy, making them the lightest gas giants ever observed.
The exoplanets, whose masses and radii were measured using data from the Kepler space telescope and follow-up ground-based observations, have densities comparable to that of the confection. Their unusually puffy atmospheres suggest they may be young and still forming, or composed of exotic materials that prevent gravitational collapse.
The discovery raises new questions about planetary formation models. Most gas giants are thought to form with dense cores, but these targets appear to lack such compaction. The findings were detailed in a recent study published in The Astrophysical Journal Letters.
One plausible explanation is that the planets have extremely extended atmospheres rich in hydrogen and helium, which expand outward due to internal heat. However, the exact mechanism behind such low densities remains uncertain, and some researchers caution that observational biases could inflate their apparent puffiness.
The system offers a natural laboratory for studying planetary interiors and atmospheric evolution. Future observations by the James Webb Space Telescope could help determine whether these super-puffs are truly anomalous or more common than previously thought.