Scientists have discovered two exoplanets, TOI-791 b and TOI-791 c, that are so low in density they have been described as lighter than candy floss or shaving foam. The findings, published in the Monthly Notices of the Royal Astronomical Society, reveal that these worlds, located 1,100 light-years from Earth, have densities 28 to 35 times lower than Jupiter. Lead author Dr. George Dransfield of the University of Oxford told Metro that while the planets are not actually edible, their density is comparable to shaving foam.
Discovery and Characteristics
TOI-791 b and TOI-791 c were first identified in 2019 and 2023, respectively, by the Planet Hunters citizen science group using NASA data. The team used the Antarctic Search for Transiting ExoPlanets telescope at Concordia Station in Antarctica to observe the planets. Dr. Dransfield noted that the extreme environment of Antarctica, devoid of life, mirrors the inhospitable nature of these exoplanets. If Earth had a similar density, it would be devoid of all life, lacking a solid surface and able to float in almost any liquid.
Rarity and Formation
Fewer than 37 of the 6,300 known exoplanets are super-puffs, and only four other systems contain multiple super-puffs. TOI-791 b and TOI-791 c orbit a yellow-white dwarf star slightly hotter and brighter than the Sun. Their low densities suggest atmospheres composed primarily of hydrogen and helium. The planets may have formed in a colder region of the protoplanetary disk, where gas was more abundant than solids, allowing them to accumulate gas without a massive core. The pair also exhibit a mean-motion resonance: for every five orbits of the inner planet, the outer completes roughly three. Their transits can last up to 11 hours, observable due to Antarctica's continuous darkness.
Implications
Dr. Dransfield emphasized that these super-puffs are extremely rare and their study could help understand planetary formation. The whimsical comparison to candy floss is a tool to make the concept accessible. 'Or cotton candy, if you're American,' she added.
