SarosZyklus

The Saros cycle, or Saros, is a period of about 18 years, 11 days, and 8 hours after which solar and lunar eclipses repeat with very similar geometry. This repeating pattern allows astronomers and historians to predict eclipses with remarkable continuity.

The cycle arises from the near-alignments of three lunar cycles: the synodic month (the lunar phase cycle, about 29.53 days), the draconic month (the nodal cycle, about 27.22 days), and the anomalistic month (the cycle between perigee and apogee, about 27.55 days). A Saros equals roughly 223 synodic months, about 6585 days, and is also close to 239 anomalistic months and 242 draconic months. Because these periods are nearly commensurate, the Sun–Moon–Earth geometry at the start of one eclipse nearly repeats after a Saros, producing a very similar eclipse type and characteristics.

However, due to the approximately 8 hours in a Saros, Earth has rotated a third of a turn. As a result, the next similar eclipse occurs at a different geographic longitude, so the eclipse path shifts westward by about one third of the globe. Solar and lunar eclipses linked by a Saros share similar geometry but may differ in location.

Historically, the term Saros comes from ancient Greek usage, and the cycle was recognized by early astronomers in Babylon and Greece as a tool for predicting eclipses. The concept remains a foundational, though approximate, connector in the history of eclipse prediction, supplemented today by precise orbital models.