Book 1, Question 87
Why Do Comets Grow Tails? A Dirty Snowball Meets the Sun!
A comet is like a dirty snowball from space, made of ice, dust and rock. When a comet gets close to the Sun, the heat turns ice into gas and releases dust, and solar wind, a stream of particles from the Sun, pushes them away to make a tail. The page shows a curvy dust tail and a straighter blue ion tail. A comet's tail always points away from the Sun. With a grown-up, hold a hair dryer near a loose scarf to see how moving air pushes fabric.
From the book
Page from A Million Whys Book 1
More fun facts
- Comets are leftovers from when the solar system formed, about 4.6 billion years ago.
- Far from the Sun, a comet is mostly just a frozen center called a nucleus.
- As a comet gets close to the Sun, jets of gas can burst out of it, carrying dust along.
- Some comets come from the Kuiper Belt, a wide disk of icy objects beyond Neptune.
- Other comets come from the Oort Cloud, a huge, sphere-shaped region at the outer edge of the solar system.
- Halley's comet swings around the Sun about once every 76 years.
- The comet with the longest known orbit takes more than 250,000 years to go around the Sun just once.
Sources: NASA Space Place
Questions kids ask
Where do comets come from?
Most come from two far-away places: the Kuiper Belt beyond Neptune, and the even more distant Oort Cloud.
How often does Halley's comet come back?
About every 76 years.