Discovering the Cotton Candy Planets: A Closer Look at TOI-791
Approximately 1,110 light-years away from Earth, in the southern constellation Volans, two gas giants are orbiting a sun-like star of spectral type F. While the existence of over 8,000 known exoplanets makes such discoveries seem routine, TOI-791 b and TOI-791 c stand out due to their exceptionally low average densities.
Characteristics of TOI-791 b and c
TOI-791 b boasts a density of just 0.038 grams per cubic centimeter, while its outer neighbor, TOI-791 c, has a slightly higher density of 0.047 grams per cubic centimeter. For comparison, Saturn—the lightest planet in our solar system—has a density of 0.69 grams per cubic centimeter, and Jupiter’s density is 1.33 grams per cubic centimeter. This remarkable distinction has led the lead author Georgina Dransfeld to describe these two planets as “cotton candy,” hinting at their fluffy, gaseous compositions primarily made up of hydrogen and helium, with traces of heavier elements.
Orbital Dynamics and Mass
Both TOI-791 b and c are roughly the size of Jupiter and complete their orbits in 139 and 232 days, respectively. Interestingly, these two worlds are in a near 5:3 orbital resonance. This means that for every five revolutions that TOI-791 b makes around its star, TOI-791 c makes three. This gravitational interplay influences each planet and helps sustain their unique characteristics. TOI-791 b has a mass of only 9.5 Earth masses, and TOI-791 c has a mass of 18.6 Earth masses. In contrast, Jupiter’s mass is 318 times greater than Earth’s, illustrating just how lightweight these new discoveries are.
The Rarity of Cotton Candy Worlds
Currently, only four other exoplanetary systems are known to host multiple cotton candy planets. The formation processes of such planets remain a mystery to scientists. One hypothesis suggests that these planets formed at a greater distance from their star and migrated inward over time. This migration could result in increased atmospheric “puffiness” due to heightened solar radiation caused by their current proximity to the host star.
Implications for Future Research
The discovery of TOI-791 b and c opens new avenues for research into the composition and formation of gas giants. These “cotton candy” planets challenge existing models of planetary formation and dynamics. Understanding how they develop and evolve can provide insights into other gas giants, both within and beyond our solar system.
Conclusion
The discovery of TOI-791 b and c invites us to rethink what we know about gas giant planets. Their astonishingly low densities and unique formation histories offer a glimpse into the complexities of planetary science. As researchers continue to explore and analyze these distant worlds, we may unlock secrets that redefine our understanding of the universe.
