The Planet That Outlived Its Own Sun
The News
Astronomers just used NASA's James Webb Space Telescope to peer at a giant planet called WD 1856 b , which orbits the burned-out core of a dead star 82 light-years from Earth. The star should have swallowed the planet when it swelled up billions of years ago… but somehow it didn't. Now scientists finally know how the planet escaped.
Professor Pip stood on a grassy hilltop, his brass telescope propped on its tripod. Twilight was turning the sky deep purple, and one bright pinkish glow flickered on the horizon. He patted his lab coat pockets and pulled out — POOF — a big red balloon and a marble tied to a piece of string.
"Ah! My favorite props," he said, giving his tail a happy swish.
Mia and Leo sat cross-legged in the grass, faces upturned.
"Tonight," Pip announced, "we're going to talk about a planet that OUTLIVED its own sun."
"Outlived its sun?!" Mia gasped.
"That's impossible!" said Leo.
"Astronomers thought so too," said Pip. "But the James Webb Space Telescope just proved otherwise. There is a planet called WD 1856 b, and it orbits the leftover glowing core of a dead star, 82 light-years from here. Here's the puzzle: that star swelled up HUGE before it died. So how did the planet survive? Let me show you."
He held up the balloon and began to blow. FWOOOOP. It got bigger. FWOOOOP. Bigger. FWOOOOP. HUGE.
"Suns like ours run out of fuel eventually," Pip said. "When they do, they puff up like this balloon — into an enormous glowing ball called a red giant. Anything TOO close to the star gets gobbled up."
Leo's eyes went wide. "Gobbled up?!"
"Gobbled up," Pip nodded. "But watch this." He picked up the marble on its string and swung it in a slow wide circle around the balloon — never letting it touch. "WD 1856 b was orbiting FAR AWAY when its star swelled. Far enough to escape. It just sat out there, patient and safe."
"But then how did it get close?" Mia asked.
"Curiouser and curiouser!" said Pip, letting the balloon PHHHT — the air rushed out and it plopped onto the grass. "After the star ran out of puff, it shriveled into a tiny, hot leftover called a white dwarf. The planet, still orbiting, slowly, slowly drifted closer. Now it whips around that little dead star in just 34 hours."
Leo thought hard. "Oh! Like when the ice cream melts and the sprinkles slide down to the bottom!"
"Exactly right!" laughed Pip, adjusting his spectacles.
He looked up at the darkening sky. "Somewhere up there," he whispered, "a whole planet is still going. Even after its sun said goodbye. That is how vast and stubborn our universe can be."
Spark a Conversation
- If our own Sun swells into a red giant in five billion years, which planets do you think might survive?
- A year on WD 1856 b lasts only 34 hours. If YOUR year were only 34 hours long, how many birthdays would you have already?
- If you could name a newly discovered planet, what would you call it — and why?