The Moon · The Sun · History
Saros
Say it: SAIR-oss IPA: /ˈsɛrɑs/ noun
Saros: An eclipse recurrence interval of about 18 years, 11 days, and 8 hours, corresponding to 223 lunations.
After one saros, the Moon's phase, distance, and position relative to its orbital nodes are nearly repeated. That allows another eclipse with similar geometry.
- Example
- The two eclipses belonged to the same saros series.
- Why astronomers use it
- It organizes related eclipses and reveals the overlapping cycles behind their recurrence.
- Tiny cosmic connection
- The extra eight hours mean Earth has turned farther, so a solar eclipse does not return to the same place after one saros. The day count also depends on leap years.
Observatory The Moon The Sun History
Where to check it
Written for Cool Moon Facts in its own words; the sources cover the same idea in more depth.