Lighter than cotton candy, the two gas giants discovered around a Sun-like star called TOI-791, located over 1,110 light-years from Earth, are the first to orbit a star similar to our Sun. These two "siblings," likely born from the same disk of gas and dust that once surrounded their star, are the same size or larger than Jupiter , but 28 and 35 times less dense, respectively. The discovery, published in the journal Monthly Notices of the Royal Astronomical Society, was made by an international team led by the University of Oxford, which also included Italian researchers from the Campo Catino Astronomical Observatory (province of Frosinone), Sapienza and Tor Vergata Universities of Rome, the National Institute for Nuclear Physics in Rome, and the National Institute for Astrophysics in Cagliari.
The two planets, TOI-791 b and TOI-791 c, were discovered thanks to 1,122 days of observations over seven years by NASA's TESS space telescope . Only four other systems are currently known to host similar superlight planets, making TOI-791 an exceptionally rare laboratory for studying how these unique celestial bodies form and evolve. "Only a few of these planets are known," says Georgina Dransfield, who led the researchers, "and it's even rarer to find two in the same system. Their extremely low density makes them fascinating subjects of study."
The two gas giants are bound to each other by a rare gravitational relationship : for every five orbits completed by the innermost planet, the other completes almost exactly three. This particular configuration means that, as they orbit their star, the two planets alternately attract each other, influencing the times at which they transit the star. It is precisely these small variations that the study's authors exploited to calculate the planets' masses, thus confirming their super-lightweight structure.
(Unioneonline)
