A shooting star isn't a star

About this video

A streak of light flashes across the night sky and is gone in a second. People call it a shooting star, but it isn't a star at all. It is a tiny piece of one of the solar system's smallest members.

The Sun's family is not only the Sun and eight planets. Millions of smaller worlds go around the Sun too. Asteroids are lumps of rock and metal, most no bigger than a town, and most of them go around between Mars and Jupiter in the asteroid belt. The belt is mostly empty space: spacecraft have flown through it many times without coming near an asteroid.

Pluto was found in 1930, beyond Neptune, and called the ninth planet. But it is smaller than our Moon, and astronomers later found many more icy worlds out there. So in 2006 it became a dwarf planet: round and going around the Sun, but sharing its path with many other worlds. Ceres, the biggest asteroid, is a dwarf planet too. In 2015 the New Horizons spacecraft flew past Pluto and saw a pale plain shaped like a heart.

A comet is a lump of ice and dust a few kilometres wide, like a dirty snowball. Near the Sun its ice turns to gas, and gas and dust stream out into a tail millions of kilometres long, always pointing away from the Sun. Halley's comet comes back about every 76 years: it came in 1986 and will come again in 2061.

Space is full of grains left behind by comets. When the Earth runs into one, it burns up in the air in a flash: a meteor, or shooting star. Most are no bigger than a grain of sand. A piece that reaches the ground is a meteorite. On some nights the Earth passes through a comet's dust and you can see a meteor shower, like the Perseids around 12 August and the Geminids around 14 December.

Transcript

1. 0:00A streak of light flashes across the sky, and is gone in a second. People call it a shooting star. But it isn't a star at all.
2. 0:16The Sun's family is not only the Sun and eight planets. Millions of smaller worlds go around it too.
3. 0:27Most asteroids, lumps of rock and metal, go around between Mars and Jupiter, in the asteroid belt. And the belt is mostly empty space.
4. 0:40Pluto was found in 1930, beyond Neptune, and called the ninth planet. But it is smaller than our Moon. In 2015 a spacecraft saw a pale plain on it, shaped like a heart.
5. 0:54Astronomers found many more icy worlds out there. So in 2006 Pluto became a dwarf planet, round, but sharing its path with many others. Ceres, the biggest asteroid, is one too.
6. 1:10A comet is a lump of ice and dust, a few kilometres wide, like a dirty snowball. Most of the time it is far out in the cold.
7. 1:24Near the Sun, its ice turns to gas. The gas and dust stream out into a tail millions of kilometres long, always pointing away from the Sun.
8. 1:40Halley's comet comes back about every seventy-six years. It last came in 1986, and it will come again in 2061.
9. 1:54Space is full of tiny grains, many left behind by comets. When one hits the Earth's air, it burns up in a flash.
10. 2:04That flash is a meteor, a shooting star. Most are no bigger than a grain of sand.
11. 2:14A bigger piece that reaches the ground is called a meteorite.
12. 2:22On some nights each year, the Earth passes through a comet's dust, and you can see many shooting stars in an hour. A meteor shower.
13. 2:32Try the Perseids, around the twelfth of August, or the Geminids, around the fourteenth of December. No telescope needed.
14. 2:42Shooting stars aren't stars. They are grains from space, burning up in our air.