Glossary term: standard candle

Description: For most celestial objects, astronomers do not have information about their distance from Earth. Under those circumstances, it can be difficult to decide whether one is looking at a distant, but very bright object, or a closer and less bright object – the apparent brightness, as measured from Earth, can be the same in both cases. A standard candle is an astronomical object whose luminosity (energy emitted per unit time) can be deduced directly from observations. The object's distance can then be calculated by comparing that luminosity and the object's apparent brightness in the night sky. Important examples: Cepheids are pulsating stars where there is a relation between the pulsation period and the luminosity. Supernovae of Type Ia are bright stellar explosions where there is a relation between the maximum luminosity and the time scale on which the brightness decreases directly afterwards.

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Term and definition status: This term and its definition is still awaiting approval

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".