Astronomers have discovered two Jupiter-sized planets, designated TOI-791b and TOI-791c, orbiting a distant star, and they are lighter than cotton candy. The findings were published recently in the Monthly Notices of the Royal Astronomical Society.
The pair rank among the largest low-density exoplanets found so far, with densities far below that of Jupiter’s, as confirmed by detailed orbital analysis that reveals the planets are in resonance.
Located 1,110 light-years away, they orbit a star in the southern constellation Volans, a distance of roughly 6 trillion miles per light-year. Jupiter, in contrast, is up to 35 times denser than either of them.
“These two planets have densities comparable to a nice blob of shaving foam, fresh from the can,” said George Dransfield, the University of Oxford astronomer who led the study.
Tracking down the fluffy giants
NASA’s TESS satellite picked up the planets over the past decade, with ground-based telescopes later tracking their orbits, which is how the team figured out the extraordinarily low densities.
The worlds are probably composed mostly of hydrogen and helium, though confirmation of their chemistry will need follow-up observations with the Webb Space Telescope. Color-wise, the planets are likely white or blue depending on how much cloud cover there is in their atmospheres.
Super-puffs, as they’re called, are extremely rare. NASA’s confirmed exoplanet tally stands at nearly 6,300, with fewer than 40 qualifying as super-puffs.
The leading theory for their formation begins with a newborn star encircled by disks of gas and dust. Planets that grow in the gas-rich parts of these disks end up with unusually low densities and tend to shed even more material over time.
“Ultimately, by studying exotic systems containing rare planet types, we add further pieces to the puzzle of planet formation and learn more about our place in the cosmos,” Dransfield explained.
Source: NASA, University of Oxford, Monthly Notices, NYP