Lesson 05 – They Came from Outer Space

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Read About What Came from Outer Space


Read the vocabulary terms to understand the reading better.

Asteroids are small rocky objects that orbit the Sun.

An asteroid belt is a region of space between the orbits of Mars and Jupiter where most of the asteroids in space are found.

A comet is a small icy object in space; when a comet comes close to the Sun, the comet gives off gases and dust that produce a large glowing ball around the comet and a long tail behind it.

Meteoroids are large lumps of rock or metal that orbit the Sun.

Meteorites are space rocks that fall to Earth’s surface.

Meteors are space rocks that enter Earth’s atmosphere.

A meteor shower is a celestial event in which lots of meteors are seen.

When an object orbits, it travels in a curved path around another object in space, such as Earth or a star.

Shooting stars are very small pieces of rock or dust that create a streak of bright light when they burn up as they enter Earth’s atmosphere.


You might say a comet is a dirty snowball that orbits the Sun. This snowball is about the size of a small city! As this snowball zooms closer to the Sun, its surface begins to turn into gas. Gas and dust stream out into a tail that can spread out as far as 80 000 km.

Comets mostly stay farther away from the Sun than our planets are. You will rarely see a comet unless you use a telescope or binoculars. Halley’s Comet is the most famous comet. It swings by Earth about every 75 years. You will have to wait until 2062 to see it again.

A bright comet


These space rocks may be shaped like balls, lumpy slabs, or bricks. You find asteroids circling the Sun in the Asteroid Belt, a band that lies between the planets Mars and Jupiter.

The biggest asteroid is bigger than many Canadian provinces. One asteroid even has its own moon. Most asteroids are only about the size of a house. You need binoculars to see them.

Image of an asteroid falling

Asteroid belt


Small chunks of asteroids or old comets may become meteoroids. When these rocky bits enter Earth’s atmosphere, they become meteors. Ever seen shooting stars? Then you have seen meteors. They burn up and shoot out fiery trails as they fall. If a meteor hits our planet, it gets a new name: meteorite.

Meteors are tiny. Most are as small as grains of sand and few get as big as baseballs. At certain times of year, many meteors streak through the night sky in a meteor shower. You can see them just by gazing up on a clear, dark night.

Meteor shower in the starry night sky

To learn more about comets, asteroids, and meteors, watch the video by Learn Bright on Youtube.

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