Astronomers Just Found Planets Fluffier Than Cotton Candy

The sun was just dipping behind the hills when Professor Pip rummaged in his pockets and pulled out the strangest pair of objects: a giant pink-and-blue cloud of cotton candy on a stick, and a tiny grey pebble.

"Tonight," he said, his crooked spectacles catching the last gold light, "we're learning a magic word. The word is density."

Mia tilted her head. "Density?"

"Yes! Density is how much stuff is squished into a space. Watch." Pip held the cotton candy up high. "This is BIG." He held the pebble out. "This is SMALL. Mia, which one do you think weighs more?"

"The cotton candy!" said Mia. "It's huge!"

"Hmmm. Leo, take them both."

Leo cupped one in each paw — and his face went funny. "But… the little stone is heavier!"

"PRECISELY!" said Pip, his tail swishing in a slow loop of delight. "Big things aren't always heavy. The cotton candy is mostly air. The stone is packed tight. We say the stone is more dense."

"Now," he said, pointing up at the very first bright dot in the twilight sky, "some fellow scientists just found two GIANT planets out there, way past where we can see, that are about as big as Jupiter — and Jupiter is huge, you could fit one thousand Earths inside it. But these new planets?" He gave the cotton candy a little squeeze. "They're this fluffy."

"NO!" said Mia. "A planet can't be like cotton candy!"

"Oh my whiskers, but it can. The scientists call them super-puffs. They're made almost entirely of two gases — hydrogen and helium — barely squished at all. If you could scoop up a piece, it would feel softer than shaving foam, fresh from the can."

Leo squinted up. "What color are they?"

"Probably white or pale blue. Not pink like the candy — sorry to disappoint." Pip grinned. "And here's the wonderful part. The scientists couldn't have spotted them without help from Antarctica."

"Antarctica?!" both children said at once.

"At the bottom of our Earth, in winter, the sun never rises for months. Months and months of dark sky. So telescopes there can stare at one little star for eleven hours straight, without ever waiting for sunrise. That's how long these planets take to slide across their star — eleven hours each!"

Pip looked up at the deepening night. "Somewhere up there, two enormous fluffy worlds are drifting around their star like soap bubbles. And we know they're there because of patient eyes on a frozen continent and a clever idea about how heavy things ought to be."

He handed each child a pinch of cotton candy and a tiny pebble. "Now you try. Hold them. Feel the difference. That's the secret the planet-hunters used."