Chapter 3 — Swell and the Star That Grows Huge

Swell was a pufferfish-tween. Not a real fish, of course. Swell was a kid, but they could puff up. They wore a chunky astronaut tunic. It was warm-cream with soft red-orange stripes. Swell was small right now. But they could get much bigger. They loved thinking about stars getting old. Swell was deeply attentive to stellar aging.

Swell sat at a console in the Stellar Observation Room. Tiny lights blinked on the console. Swell held a stack of cards. These were red-giant-cards. Next to them was a stellar-evolution-tracker. It showed how stars changed over time. Swell watched it intently.

“Oh, dear,” Swell mumbled. Their eyes were glued to the screen. A tiny dot on the tracker, labeled ‘Sun-like Star,’ started to flicker. “It’s happening.”

“What’s happening?” asked Pip, who was trying to untangle a knot in their space-boot laces nearby. Pip wasn’t really paying attention.

Swell spun around. Their tunic rustled. “The star! It’s running out!” Swell held up a card. It showed a bright, yellow star. “This is a main-sequence star. Like our Sun, right now. It’s happy. It’s burning hydrogen.”

Pip finally looked up. “Burning hydrogen? Like a campfire?”

Swell shook their head. “Not exactly. It’s fusion. Deep inside the star. It makes light and heat.” Swell tapped the card. “But stars don’t have endless fuel. Nothing does, really.”

Swell’s voice dropped. “Hydrogen runs out.” Swell pushed the first card aside. They picked up another. This one showed a star with a tiny, bright center. The edges looked fuzzy. “When the hydrogen in the core is gone, the core contracts.” Swell pulled their arms in tight to their chest. They looked like a tiny, round ball.

Then, Swell took a deep breath. Their cheeks puffed out. Their chunky astronaut tunic stretched. It strained a little at the seams. Swell’s whole body began to expand. Slowly at first, then faster. “And the outer shell expands!” Swell’s voice was a bit muffled now. They were getting bigger. Much bigger.

The stellar-evolution-tracker on the console beeped. The tiny dot on the screen grew. It turned a deep, fiery red. Swell was now almost twice their original size. Their red-orange stripes seemed to glow.

“Whoa!” Pip exclaimed. They scrambled back a bit. Swell was taking up a lot of space.

Swell pointed a chubby finger at the tracker. “See? The star gets huge. It turns into a red giant.” Swell held up another card. This one showed a massive, red, glowing orb. It was enormous. It dwarfed the other stars on the cards. “It can be a hundred times bigger than it was before.”

Swell took another breath, puffing up even more. Their tunic was really stretching now. “The core gets super hot. Hotter than ever!” Swell’s face was bright red with effort, or maybe just excitement. “Hot enough to start fusing helium!”

“Helium?” Pip asked. “Like in balloons?”

Swell nodded, still expanding. “Exactly! Helium fusion begins. It’s a whole new way for the star to make energy.” Swell let out a little puff of air. They were truly enormous now. They almost touched the ceiling of the Stellar Observation Room. Their voice echoed a bit. “This is the red giant phase.”

Swell looked around the room. Their giant eyes seemed to take everything in. “Our own Sun will do this. In about five billion years.” Swell paused. “It will swell up. It will get so big, it will swallow Mercury. Then Venus. And then… Earth.”

Pip’s jaw dropped. “Swallow Earth? Our Earth?”

Swell nodded slowly. They started to shrink a little. The air hissed out of them gently. Their tunic relaxed back to its normal size. “Yep. It’s just what happens. Stars get old. They change.” Swell was back to their small, normal size. They looked a bit tired, but still deeply fascinated. Swell was fond of saying it: “Hydrogen runs out. Core contracts. Shell expands. Helium fusion begins.”

Swell carefully placed the red giant card on top of the stack. They looked at the stellar-evolution-tracker. The red dot was still there, glowing. “It’s a big change. A really, really big change.”

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