Glossary term: Mirror

Description: A mirror is an optical device that reflects light from its surface. Convex mirrors spread beams of light out and concave mirrors focus parallel beams of light to a point. Most modern telescopes use large concave mirrors are their primary collecting area. The main body of most mirrors used in astronomical telescopes is made of glass. This is ground and polished into the correct shape and given a thin reflective metal coating. As telescopes grew in size the technical challenges of casting and supporting huge glass mirrors grew. As a result, some of the largest telescopes in the world now use many smaller mirrors that are arranged together to focus light as if they were one giant mirror.

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The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".