Saros (astronomy)

The saros (/ˈsɛərɒs/ ^ⓘ) is a period of exactly 223 synodic months, approximately 6585.321 days (18.04 years), or 18 years plus 10, 11, or 12 days (depending on the number of leap years), and 8 hours, that 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. A sar is one half of a saros.^[1]

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

• 6,585.321347 solar days
• 18.029 years
• 223 synodic months
• 241.999 draconic months
• 18.999 eclipse years (38 eclipse seasons of 173.31 days)
• 238.992 anomalistic months
• 241.029 sidereal months

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.