Astronomers Identify Largest Super-Puff Planets Found to Date

Astronomers have identified two giant planets with densities lower than cotton candy, making them the largest and lightest known exoplanets of this type. The planets orbit a star in the southern constellation Volans, 1,110 light-years from Earth. One completes an orbit in 139 days and the other in 232 days.

TESS satellite detected both worlds over the past decade. Researchers used ground-based telescopes to determine the planets’ densities from that distance. A light-year equals nearly 6 trillion miles. The pair are the biggest exoplanets found with densities lower than cotton candy and the lightest known planets of their size.

The planets have densities comparable to shaving foam.

They are likely composed mostly of hydrogen and helium and probably appear white or blue depending on cloud cover. Jupiter is up to 35 times denser than either planet. Fewer than 40 of the nearly 6,300 confirmed exoplanets are classified as super-puffs.

"The main reason these planets are interesting to study is that we didn't expect to see them at all," said Jon Jenkins, science lead for the Science Processing Operations Center at NASA’s Ames Research Center. "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," George Dransfield of the University of Oxford said.

The research team published its findings Wednesday in Monthly Notices of the Royal Astronomical Society.