Science for Kids — August 20: Fastest stars, golden trees underwater, and a shark that glows

Professor Pip stood on the hilltop, his spectacles slipping down his nose. He patted the bulging pockets of his forest-green lab coat and pulled out a small brass telescope, a marble, and a long piece of string.

"Ah!" he said, tail swishing. "Just the things."

Mia, Leo, and their friend Asha sat cross-legged on the grass. Overhead, the Milky Way spilled across the night sky like sugar poured across black velvet.

"Tonight," Pip announced, "we're going to talk about the fastest star anyone has ever found. Astronomers just spotted it — a little star called S301 — and it zooms around a giant black hole at the center of our galaxy."

"A black hole?!" Leo whispered.

"A very hungry one," Pip nodded. "Its name is Sagittarius A-star. It has four million times the mass of our Sun, all squished into one tiny spot. And here's the tricky question: how does a star zoom around something you can't even see?"

He set a black rubber ball on the grass. "Pretend this is the black hole." He tied the marble to the string and held the other end in his paw. "And this marble is S301."

Pip started spinning the marble in a wide circle around the ball. WHIRR! The marble whipped past the children's toes.

"Now watch what happens when I hold the string closer." He wound the string shorter, and the marble zipped faster and faster. WHOOSH-WHOOSH-WHOOSH!

"It's going super fast!" Asha gasped.

"Precisely!" Pip beamed. "The closer something orbits a big heavy object, the faster it has to go so it doesn't fall in. That pull is called gravity. S301 comes so close to the black hole that its top speed is 25,000 kilometers every second — fast enough to zip across the whole United States in less time than it takes you to blink."

"Oh!" said Mia. "It's like when I swing a bucket really tight in a circle — the water gets pressed against the bottom and it goes zoom!"

"Exactly right!" Pip's tail thumped with delight. "By watching S301 loop around, scientists can finally measure how fast the black hole itself is spinning. That's a puzzle no telescope has solved before."

Pip tucked the marble away and looked up at the Milky Way. "Somewhere up there, right now, S301 is racing around a giant we cannot see. Isn't the universe curious?"

"Curiouser and curiouser!" cried Professor Pip, patting his pockets on a rocky beach at sunset. He pulled out a magnifying glass, a small notebook labeled "Notes," and — with a great deal of tail-swishing — a wide glass tank sloshing with dark blue water.

Mia and Leo peered in. Inside, Pip had arranged a bright yellow branching model, no bigger than a teacup, shaped like a tiny tree. All around its base, dozens of pipe-cleaner brittle stars huddled together.

"Ah! Meet the newest creature on Earth's family tree," Pip said. "Scientists just found it deep under the ocean. It's called Laurinque — a golden-tree coral."

"It looks like a real tree!" Leo said.

"It looks like a tree, yes — but here is the wondrous bit." Pip held up his magnifying glass. "A coral is not a plant at all. A coral is a giant apartment building made of thousands of tiny animals called polyps. Each polyp is a wee squishy creature with waving arms, and together they build a hard, branching home."

Mia leaned in, wide-eyed. "So the whole gold tree is made of… animals?"

"Precisely! Thousands of them, all cousins, all growing together." Pip's spectacles slipped as he grinned. "Now, when the scientists pulled up this coral's DNA — that's the little instruction book inside every living thing — they got a shock. Its instructions didn't match any coral family we know. It was so different that they had to invent a brand-new family, just for it!"

He tapped the tank. "And around its trunk live these bendy little brittle stars — cousins of sea stars, with five whippy arms."

"Oh!" said Leo. "It's like finding a new kind of dog that isn't a labrador OR a poodle — you'd need a whole new dog family for it!"

"Exactly right!" Pip clapped his paws. "That is taxonomy — sorting living things into family groups. And this golden tree is telling us the deep ocean is still hiding relatives we've never met."

Pip looked out over the water as the last light shimmered on the waves. "There are creatures down there right now that no human being has ever seen."

He handed each child a magnifying glass. "Now I wonder — what tiny bit of nature lives right in your backyard that no one has looked at closely yet?"

"Everyone, into the dark corner of the lab!" cried Professor Pip. He turned off the overhead light and pulled out his pocket notebook, a glow-stick, and a paper shark he'd cut out that morning.

Mia, Leo, and Beatrix shuffled into the shadows, giggling.

"Today," Pip announced, spectacles flashing, "we're solving a shark mystery. Deep in the ocean lives the kitefin shark. It's as long as a grown-up — the largest glow-in-the-dark animal with a backbone we know of. But why would a shark want to shine?"

"So its friends can find it?" Leo guessed.

"A lovely guess! But watch." Pip held the paper shark up on a string and clicked on a small flashlight above it, pointing down. "Pretend this flashlight is the Sun shining down into the ocean." He tilted his head. "Now, look up at the shark from below."

The children lay on the floor and peered up. Against the light, the paper shark was a big dark silhouette — an easy shape to spot.

"A yummy shape for a fish to see and swim away from," Pip said. "Now — my whiskers! — watch this trick." He snapped the glow-stick. CRACK! A soft green glow spread across the paper shark's belly.

"It disappeared!" gasped Beatrix.

"Precisely!" Pip clapped. "The glow from below matches the light from above. From a little fish looking up, there is no shadowy shark shape at all. That trick is called counter-illumination. The kitefin shark's belly has millions of teeny lights called photophores that glow at just the right brightness."

"Oh!" said Mia. "It's like camouflage — but with light instead of paint!"

"Exactly right!" Pip's tail thumped. "And here is the marvelous twist scientists just discovered: the shark's glow is extra bright out to the sides. That side-glow acts like a soft searchlight, helping the shark spot yummy squid and fish. So its light hides and hunts, all at once."

Pip looked at his glow-stick and sighed happily. "Nature is such a clever inventor. Every problem — being seen, finding food — has a beautiful solution somewhere."

He handed each child a small glow-stick to take home. "Now you try, in your own dark room tonight. And I wonder… what other animals do you know that light up?"