TESS reveals the puffiest planets ever found

Data from NASA’s TESS mission has revealed two new "super-puff" planets — giant worlds so light their density is comparable to cotton candy. The planets orbit a Sun-like star named TOI-791 about 1,113 light years from Earth. Identified as TOI-791 b and TOI-791 c, they are described as the "puffiest" worlds ever found.

TOI-791 b is nearly the same size as Jupiter but contains just 3.0 percent of Jupiter’s mass, while TOI-791 c is larger than Jupiter yet holds only 5.9 percent of Jupiter’s mass. Both have unusually long orbits, with TOI-791 b taking 139 days and TOI-791 c taking 232 days to circle their host star.

TESS first detected the planets by watching for repeated dips in TOI-791’s brightness, a telltale sign that a planet is transiting, and collected 1,122 days of data on the system over seven years. Further analysis showed the two planets are locked in an orbital pattern that lets them tug on each other, producing variations in the timing of their transits.

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