A 12-Billion-Year-Old Snowball Just Zoomed Through Our Sky
The News
Astronomers using NASA's James Webb Space Telescope just figured out something amazing about a comet called 3I/ATLAS that visited our solar system last year. After studying the chemicals in its icy "tail," scientists think this comet may be 10 to 12 billion years old — almost as old as the universe itself, and nearly three times older than our Sun. It came from a totally different star, in a very cold corner of our galaxy.
Professor Pip adjusted his slightly crooked spectacles and squinted up at the deepening sky. The first stars were beginning to wink on above the hilltop. "Ah! Perfect timing," he said, patting his bulging green lab coat until he found what he needed — a small, frosty snowball, tucked in beside his brass telescope.
Mia and Leo sat cross-legged on a picnic blanket, looking up.
"Tonight," Pip whispered, his fluffy tail swishing, "we are going to think about something very, very old."
"How old?" asked Mia.
"Older than this hill. Older than the ocean. Older than… our Sun." Pip's tail swished again. Mia and Leo's mouths popped open.
"Older than the Sun?" Leo gasped.
Pip held up the small snowball. "This snowball is just from yesterday's weather, fresh and easy. But out beyond the planets, way past the cold black where light is faint, there are snowballs that have been frozen for billions of years. They drift, slow and quiet, sometimes spiraling toward a sun. We call those — comets."
A single soft streak of light slipped across the sky.
"Just like that one," Pip whispered. "When a comet swings close to the Sun, the ice warms up and turns to gas. That glowing tail is the comet's old, old chemicals — finally waking up. So a comet," he said, pointing his pencil at the sky, "is a time capsule. The ice inside has been frozen since before the Sun was even born."
"Like a sandwich in the back of the freezer!" said Mia, eyes shining. "It still tastes the same forever, because it never warmed up!"
"Precisely right!" Pip beamed. "Last year, a comet called 3I/ATLAS visited us from another star. The James Webb Space Telescope tasted its chemicals — and they were so old, so different, that scientists think it formed almost twelve billion years ago. Long, long, long before our Sun."
Pip looked up. "Somewhere out there, while dinosaurs hadn't even been imagined, that little snowball was already drifting." He pulled out his pocket notebook and a pencil. "Now — draw it for me. Draw what an ancient traveler looks like."
Spark a Conversation
- If you could send a "time capsule" into space, what would you put inside?
- Comets are kept the same because they are frozen for billions of years. What else stays the same when it's frozen?
- If a comet brought ice all the way from another star, do you think it could be carrying anything else?