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In the night sky: Orion
In the night sky: Orion

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Orion Glossary

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magnitude scale

An historical, logarithmic scale devised to represent the observed brightness of astronomical objects such as stars.

main sequence

The portion of the lifetime of a star during which it produces energy via the fusion of hydrogen to helium in its core. A star will remain on the Main Seqeunce for the majority of its total lifetime.


Extra-terrestrial object that is observed by the electromagnetic radiation it emits as it enters the Earth's atmosphere. 'Shooting stars' are visible meteors.


An extra-terrestrial rock (generally a fragment of an asteroid) that has fallen to the Earth’s surface.