πͺ Two Giant Planets Lighter Than Cotton Candy
The News
Astronomers using NASA's TESS space telescope just announced the two biggest "super-puff" planets ever found. They orbit a faraway star called TOI-791, about 1,110 light-years from Earth in the constellation of the Flying Fish. Both planets are the size of Jupiter β but so unbelievably fluffy that if you could scoop up a chunk, it would weigh less than the same-sized chunk of shaving cream. Astronomers say Jupiter is up to thirty-five times denser than these new lightweights.
Professor Pip's lab smelled, unexpectedly, of sugar. He was standing at his workbench, tail swishing with excitement, holding a fluffy pink cloud of cotton candy in one paw and a small grey pebble in the other.
"Fellow scientists," he said, pushing his crooked spectacles up his nose, "close your eyes and pick a paw."
Leo pointed at the cotton candy. Mia pointed at the pebble.
"Heft them," said Pip, handing over. "Which one is heavier?"
"The pebble!" said Mia. "By SO much."
"But they're almost the same size," said Leo, squishing the cotton candy suspiciously.
"Exactly right!" Pip beamed. "That difference has a special name. We call it density β how tightly packed the little pieces of a thing are. A pebble has its bits jammed up close together. Cotton candy is mostly air, puffed up with just a little sugar."
He turned to the big brass telescope tilted toward the window. "Now β imagine an entire planet made mostly of air."
"WHAT?" said both children at once.
"Astronomers just found two of them, one thousand one hundred and ten light-years away. Each one is as big as Jupiter β huge! β but so wispy and fluffy that if you cut out a piece, it would feel like a puff of shaving foam fresh from the can. Not even hydrogen and helium gas can hold itself together very tightly out there."
Mia's eyes went wide. "So if I went there, I'd just⦠sink through it?"
"Oh my whiskers, that IS the marvelous question," said Pip. "The gas would get thicker as you fell β first like fog, then like syrup, then like honey. But at the very top? Yes. You'd sink like a stone falling into a bowl of pancake batter. Slowly. Slowly. Slowly."
"So they're PLANET-shaped clouds," said Leo. "Like⦠cosmic marshmallows."
"Precisely!" Pip clapped his paws. "Astronomers call them super-puffs. Out of nearly six thousand three hundred planets we've found beyond our solar system, fewer than forty are like this. They're probably white or pale blue. Never pink, sadly." He gave the cotton candy one last regretful look.
He set the pebble and the fluff side by side on the desk. "The universe made two things the same size, but one is so much lighter than the other. That means the universe is thinking in densities β and now, so are we."
He handed each child a small feather and a small pebble. "Off you go. See how many things around your house are secretly puffier than they look."
Spark a Conversation
- What's something in your house that looks big but weighs almost nothing? What's something small but really heavy?
- If a planet is mostly gas, what do you think its "surface" would feel like as you got deeper?
- Only 40 super-puff planets have ever been found. Why do you think they're so rare?