In astronomy, a celestial coordinate system is a system for specifying positions of celestial objects: satellites, planets, stars, galaxies, and so on. Coordinate systems can specify a position in 3-dimensional space, or merely the direction of the object on the celestial sphere, if its distance is not known or not important.
The celestial equivalent of latitude is called declination and is measured in degrees North (positive numbers) or South (negative numbers) of the Celestial Equator. The celestial equivalent of longitude is called right ascension.
The most popular celestial coordinate system is the equatorial coordinate system. The variant most suitable for values that are only updated occasionally is the International Celestial Reference System. The origin of the coordinate system is the barycenter of the solar system, which for most purposes is equivalent to the center of the Sun. Similarly to the geographic coordinate data type, it requires two angles, right ascension and declination. The nomenclature for right ascension is a bit different from longitude, using hour angles (hours ( h ), minutes ( m ), and seconds ( s )) instead of degrees (degree, (°) minute ('), second ('')), which means that a circumference is 24h instead of the customary 360°.