Two newly confirmed super-puff planets, each about the size of Jupiter but less dense than cotton candy, have been discovered orbiting a distant star 1,110 light years away, marking an exceptionally rare find in the search to understand unusual worlds in our galaxy.
- Planets are roughly Jupiter-sized but exceptionally low in density
- Orbit their star in a rare 5:3 mean-motion resonance
- Observed in uninterrupted long transits from Antarctica
What happened
An international team led by the University of Oxford has confirmed two exceptionally fluffy giant planets, TOI-791 b and TOI-791 c, with densities so low that they are even less dense than cotton candy. These planets orbit an F7-type dwarf star located about 1,110 light years away in the constellation Volans. Each planet is approximately the size of Jupiter but has a fraction of its density—TOI-791 b measures at 0.038 grams per cubic centimeter and TOI-791 c at 0.047 grams per cubic centimeter, compared to Jupiter’s 1.33 grams per cubic centimeter.
The two planets were initially spotted by volunteers in the Planet Hunters TESS project and later studied using data from various telescopes, including the ASTEP telescope in Antarctica. Their discovery is notable not only for their extreme low density but also because they orbit their star in a rare 5:3 mean-motion resonance, meaning for every five orbits the inner planet completes, the outer completes almost exactly three. This results in ongoing gravitational interactions that affect their transit timing.
Why it feels good
Discovering such rare super-puff planets offers scientists a unique window into understanding planetary formation and evolution, especially about how planets acquire and sustain extremely large, lightweight atmospheres. These planets challenge the conventional view that giant planets must be dense, providing a striking example of how diverse planetary systems can be across the galaxy.
The long, uninterrupted observations enabled by Antarctica’s continuous darkness allowed astronomers to capture the longest fully observed planetary transits from the ground, setting a new benchmark for detailed study. This thorough data collection enriches scientific knowledge and inspires public fascination with the cosmos, reminding us of the vast variety and unexpected nature of worlds beyond our solar system.
What to enjoy or watch next
Researchers will continue studying the TOI-791 planets to uncover how such lightweight atmospheres form and how these planets have maintained their rare orbital resonance. Watching for further discoveries of super-puff planets in other systems may soon expand our understanding of planetary diversity and atmospheric development in different stellar environments.
Future missions and ground-based telescopes, aided by citizen science projects like Planet Hunters TESS, are expected to reveal more unusual exoplanets and offer new clues. For science enthusiasts and space lovers, following these discoveries as they unfold promises an exciting opportunity to witness the unveiling of some of the most extraordinary and delicate planets known.