Saros (astronomy)

In astronomy, the saros (/ˈsɛərɒs/ ⓘ) is a length of time covering exactly 223 synodic months (18 years 11 days and 8 hours), 242 draconic months and 239 anomalistic months. Arising naturally due to synchronization between lunar phase, nodal precession, and apsidal precession, it can be used to predict eclipses of the Sun and Moon. One saros period after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, a near straight line, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle. Every eclipse has an associated saros series and all succeeding or preceding eclipses have a different saros series associated with them - as the eclipse of the same series occurs or occurred with a gap of one saros only. Solar and lunar eclipses have different saros series.

A series of eclipses that are separated by one saros is called a saros series. It corresponds to:

The 19 eclipse years means that if there is a solar eclipse (or lunar eclipse), then after one saros a new moon will take place at the same node of the orbit of the Moon, and under these circumstances another solar eclipse can occur.


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