## Glossary term: Degree

Description: In mathematics a degree (symbol °) is a measure of angle. One degree is 1/360th of a full circle. It can be expressed as a decimal number or it can be divided into arcminutes (symbol ′) where 60′ is 1°, and arcseconds (symbol ″) where 60″ is 1′. One arcsecond is 1/3600th of a degree, an extremely small angle.

Degrees measure the apparent size of an object (see angular diameter) and its position on the celestial sphere. See also: declination, right ascension, altitude, and azimuth. On Earth: latitude and longitude. They are also used to measure angular distance between objects on the celestial sphere. The width of your fist at arm’s length is about 10°; from the horizon to the zenith is 90°. Depending on the scale, a telescope’s resolution and field-of-view can be expressed in degrees, arcminutes, or arcseconds.

Alternate meaning: A unit in the measure of temperature, used with the Fahrenheit or Celsius scales. The Celsius scale is defined by the freezing point of water at sea level being 0°C and the boiling point of water being 100°C. A change of one degree Celsius is the same as a change of one kelvin but they have different zero points. The zero point of the kelvin scale is absolute zero, the lowest temperature, -273.15°C. In the older Fahrenheit system a change of one degree is the same as a change of 5/9ths of a degree Celsius or kelvin.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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