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The Universe

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What is the Universe?

The Universe is defined as ‘everything that exists’. It contains:

The Universe contains thousands of millions of galaxies. Each galaxy contains thousands of millions of stars.

Our Solar System is part of a galaxy known as the Milky Way. It is thought that the Milky Way contains between 100–400 billion stars, of which our Sun is just one.

planets stars comets and asteroids black holes galaxies.

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Celestial bodies in the Universe

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The observable Universe

The observable Universe refers to everything that is in the Universe that we theoretically could see.

This includes any object whose light has had time to reach the Earth since the beginning of the Universe. It is likely that most of the observable Universe has not yet been seen.

Even the light that we see from the nearest galaxy to ours, the Andromeda Galaxy, originated about 2.5 million years ago.

The Hubble Space Telescope is able to see galaxies from when the Universe was only 400 million years old.

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The size of the Universe

To find the Sun within that grain of dust would be like finding one particular grain of sand in a seven-metre-wide circular pool filled with sand!

When thinking about the Universe, it can be difficult to understand the size and scale that is involved.

If the observable Universe was scaled down to the size of Earth, our galaxy would be the size of one micron – roughly the size of a small piece of dust.

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Journey through the Universe

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Distances in the Universe

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If the Sun…