Syzygy (astronomy)

A syzygy occurs during eclipses (numbers 1, 2, 3, 4).

In astronomy, a syzygy (/ˈsɪzədʒi/ SIZ-ə-jee; from Ancient Greek συζυγία (suzugía) 'union, yoking', expressing the sense of σύν (syn- "together") and ζυγ- (zug- "a yoke")[1][2]) is a roughly straight-line configuration of three or more celestial bodies in a gravitational system.[3]

The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations. The term is often applied when the Sun and Moon are in conjunction (new moon) or in opposition (full moon).[4]

When Earth is one of the bodies involved, the other objects appear to be close together (or overlapping) in the sky.

Jupiter (top), Venus (lower left), and Mercury (lower right) above La Silla Observatory, Chile (May 26, 2013)[5]
  1. ^ "syzygy". CollinsDictionary.com. HarperCollins. Retrieved 22 August 2012.
  2. ^ "syzygy". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ "Syzygy". Glossary, The Astronomical Almanac Online. HM Nautical Almanac Office and United States Naval Observatory. 2012. Archived from the original on 2013-06-15. Retrieved 2012-09-13.
  4. ^ Coyle, Harold P. (2008). "Syzygy". AccessScience. ©McGraw-Hill Companies. doi:10.1036/1097-8542.757218. Retrieved May 5, 2012.
  5. ^ "Three Planets Dance Over La Silla". ESO Picture of the Week. Retrieved 5 June 2013.