The featherweight pair — orbiting a star 1,110 light-years away — are the biggest exoplanets found to have less density than cotton candy.
That makes them the lightest known planets of their size, said the University of Oxford’s George Dransfield.
“These two planets have densities comparable to a nice blob of shaving foam, fresh from the can,” Dransfield said in an email. She and her team reported their findings Wednesday in Monthly Notices of the Royal Astronomical Society.
Dransfield suspects these fluffy, wispy worlds are probably white or blue, depending on whether the skies there are cloudy — no shades of cotton-candy pink. The planets are probably mostly hydrogen and helium, although it will take follow-up observations by NASA’s Webb Space Telescope to confirm their chemical makeup.
Detected by NASA’s Tess satellite over the past decade, these two especially puffy-puffs orbit a star in the southern constellation Volans, known as the flying fish. The researchers studied the planets’ orbits using telescopes on Earth to determine their density, from 1,110 light-years away. A light-year is nearly 6 trillion miles (9.7 trillion kilometers).
Jupiter, by comparison, is as much as 35 times denser than these two lightweights.
Considered rare in the cosmos, super-puffs are thought to form around the disk of gas and dust around a newborn star where there is more gas than dust. They shed much of the material over time, stripping down even more.
NASA’s tally of worlds outside our solar system currently stands at nearly 6,300 confirmed. Fewer than 40 are super-puffs, according to Dransfield.
“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,” she said.
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