Overview
- An Oxford-led study published on Wednesday measured the masses of TOI-791 b and TOI-791 c and reported that each planet has only a few percent of Jupiter's mass, making them unusually light for their size.
- The team used transit-timing variations seen in TESS data, with supplementary observations from the ASTEP telescope in Antarctica, to derive the planets' masses from their mutual gravitational pulls.
- Measured bulk densities are extremely low at about 0.038 g/cm³ for TOI-791 b and 0.047 g/cm³ for TOI-791 c, values comparable to or below the density of cotton candy and far below normal gas-giant densities.
- Authors propose two leading explanations—envelope inflation by the host star's radiation or formation in cold outer regions with later inward migration and ice vaporization—and have called for JWST spectroscopy to discriminate between them.
- Finding two extreme Super-Puffs in the same system makes TOI-791 a rare testbed that could force revisions to simple planet-formation and migration models and guide where astronomers target future atmospheric studies.