Concept information
Preferred term
Sunspots
Definition
- An area seen as a dark patch on the Sun's surface. Sunspots appear dark because they are cooler (of about 4000 °C) than the surrounding photosphere (about 6000 °C). They range in size from a few hundred kilometers to several times the Earth's diameter and last from a few hours to a few months. Very small sunspots are called pores. The number of sunspots varies from maximum to minimum in about 11 years, the sunspot cycle. Their appearance during a cycle follows the Sporer law. A typical spot has a central umbra surrounded by a penumbra, although either features can exist without the other. Sunspots are associated with strong magnetic fields of 0.2 to 0.4 tesla. A given sunspot has a single magnetic polarity. The opposite polarity may be found in other sunspots or in the bright and diffuse facular region adjacent to the sunspot. The first recorded naked-eye sightings of sunspots were by Chinese astronomers in the first century B.C. Johannes Fabricius (1587-1617) was the first to argue that sunspots are areas on the solar surface. (en)
Broader concept
- Solar active regions (en)
- Solar physics (en)
Narrower concepts
- Delta sunspots (en)
- Ephemeral active regions (en)
- Maunder minimum (en)
- Sunspot flow (en)
- Sunspot groups (en)
- Sunspot number (en)
- Wilson effect (en)
Entry terms
- Sun spots (en)
Editorial note
URI
http://astrothesaurus.org/uat/1653
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