Two Planets as Fluffy as Cotton Candy

Professor Pip pushed his crooked spectacles up his nose and patted the bulging pockets of his forest-green lab coat. "Ah! Just what today calls for," he said, and out came the strangest pair of things: an enormous pink cloud of cotton candy on a wooden stick, and one small grey pebble.

Mia, Leo, and their friend Sofia sat cross-legged on a picnic blanket in the forest clearing, blinking.

"Professor Pip," said Sofia, "why do you have snack food AND a rock?"

"Because, my fellow scientists," Pip said, tail swishing, "astronomers have found two planets that are as big as Jupiter — but as fluffy as this." He held up the cotton candy.

"WHAT?" Leo laughed. "Planets can't be fluffy!"

"Curiouser and curiouser, isn't it?" Pip beamed. "Here. Feel." He handed Sofia the cotton candy and Mia the pebble. "Which one feels heavier?"

"The rock, obviously," said Mia.

"Precisely! Now — if I made a rock the size of your head and a cotton candy the size of your head, the rock would still be much, much heavier. That's called density. How much stuff is squeezed into a certain space."

Pip pulled out his pocket notebook. "These two new planets orbit a star called TOI 791. One weighs about the same as nine and a half Earths. The other, about eighteen Earths. That sounds like a lot — until you learn that Jupiter, which is only a little bigger than these planets, is 317 times heavier than Earth!"

Sofia squished the cotton candy. "So the planets are big but almost… empty?"

"Oh! Like a beach ball!" said Leo. "Big on the outside, mostly air inside."

"Exactly right!" Pip cried, tail wagging. Astronomers call them superpuffs. Scientists think these planets might have been born far from their star, then wandered in closer. As they warmed up, their atmospheres puffed out like popcorn — making them huge but incredibly light. Next, the James Webb Space Telescope will sniff their air to figure out what they're made of.

Pip looked up through the trees at the pale afternoon sky. "Somewhere out there, right now, two enormous fluffballs are floating around a distant star. Isn't the universe a delightfully strange kitchen?"

Then he handed each child a piece of cotton candy. "Now you try. Squeeze it, feel it, weigh it in your paw. That's what a superpuff planet would feel like in the palm of your hand."