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1. The Parts of the Solar System

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We live on the planet Earth

Vocabulary

Planet

A large, solid object that travels around a star

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Earth is one of nine planets circling a star we call the sun

The sun and the nine planets make up our

solar system 4

Vocabulary

Solar system

The sun and the nine planets

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The most common theory of how the solar system was formed was by circulating

gases and dust

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A chemical reaction occurred with heat

to cause an explosion causing objects to form during cooling

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Video Birth of a Solar System

Each of the nine planets move in an orbit around the sun

Vocabulary

Orbit

A curved path that each of the planets moves

around the sun9

The size of a planet’s orbit depends on the distance of the

planet from the sun

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Closer planets have smaller orbits.

Planets far from the sun have large orbits

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Mercury Venus Earth Mars

All the planets are held in orbit by a force called gravity

Vocabulary

Gravity

A force that acts like a pull between the sun and

planets12

Without gravity, the planets would drift into space

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The space shuttles sent to space by NASA are held into

orbit around the Earth by gravity

Some planets have smaller objects called moons

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Vocabulary

Moons

A small object in orbit with a planet

There are more than 50 moons orbiting the planets of the solar

system

Each moon is held in orbit by the gravity between the moon

and its planet

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One moon orbitsEarth

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Asteroids and comets are smaller objects in the solar

system

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Vocabulary

Asteroids

An object made of rock and metal that orbits the

sun

Asteroids orbit the sun in a belt between the planets Mars

& Jupiter

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Vocabulary

Comet

An object made of ice, gas, and dust that orbits

the sun

A comet has a bright fiery head and a long tail of light

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Comets have very large orbits and travel to the edge of the

solar system