NASA Telescope Finds Two Jupiter-Sized Planets as Light as Cotton Candy

NASA’s TESS space telescope has identified two unusual exoplanets in a distant solar system, TOI-791 b and TOI-791 c, both about the size of Jupiter but with extremely low mass. Their density is so low that NASA scientists compare it to cotton candy, making them among the “puffiest” planets known.

The planets were found by a team led by George Densfield of the University of Oxford’s Department of Physics, using data gathered by TESS. TOI-791 b is almost identical to Jupiter in size but has only about 3% of Jupiter’s mass. TOI-791 c is even larger than Jupiter, yet its mass is only about 5.9% of Jupiter’s. Densfield said only a handful of such planets are known, and finding two in the same system is especially unusual.

Steve Howell of NASA’s Ames Research Center said giant planets play a major role in how solar systems evolve, so studying Jupiter-sized planets with much lower mass could reveal important clues about how they form. TESS, launched in 2018 to find nearby exoplanets, has so far identified 7,931 planet candidates, of which 897 have been confirmed.

In the TOI-791 system, researchers relied on 1,122 days of observations collected over seven years. The data showed the planets have very long orbital periods and exert gravitational pulls on each other, causing tiny changes in the timing of their transits across their star. Those transit variations allowed the team to calculate their masses. The researchers now hope to learn more about the chemical makeup of the planets’ atmospheres, how their rotation affects their shape, and how planets with such extremely low density are formed.