Astronomers have discovered a pair of giant planets that are lighter than cotton candy – “super-puffs” the size of Jupiter.
The featherweight pair, dubbed TOI‑791 b and TOI‑791, orbit a star 1,110 light-years away, and 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,” Dr Dransfield said in an email.
Their densities are lower than that of candy floss, which is about 0.05 grams per cubic centimetre.
In comparison, Earth’s density is 5.5 grams per cubic centimetre, more than 100 times greater, researchers say.
Scientists reported their findings on Wednesday in the journal Monthly Notices of the Royal Astronomical Society.
Dr 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.
Researchers studied the planets’ orbits using telescopes on Earth to determine their density, from 1,110 light-years away. A light-year is nearly 9.7 trillion kilometres.
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.
Both the newly discovered planets likely formed from the disc of gas and dust surrounding their young star, making them “siblings”, researchers say.
Nasa’s tally of worlds outside our solar system currently stands at nearly 6,300 confirmed. Fewer than 40 are super-puffs, according to Dr Dransfield.
Scientists are still unclear how such planets form.
A leading theory suggests that they possess vast hydrogen- and helium-rich atmospheres that accumulated rapidly around a solid core.
“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,” Dr Dransfield said.
