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This article is about astronomical eclipses. For other uses, see Eclipse (disambiguation).
"Total eclipse" redirects here. For other uses, see Total Eclipse (disambiguation).
Totality during the 2000 solar eclipse. Solar prominences can be seen along the limb (in red) as well as extensive coronal filaments.

An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer. An eclipse is a type of syzygy.[1]

The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the Earth's shadow. However, it can also refer to such events beyond the Earth–Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host planet, or a moon passing into the shadow of another moon. A binary star system can also produce eclipses if the plane of the orbit of its constituent stars intersects the observer's position.


The term is derived from the ancient Greek noun ἔκλειψις (ékleipsis), which means "the abandonment", "the downfall", or "the darkening of a heavenly body", which is derived from the verb ἐκλείπω (ekleípō) which means "to abandon", "to darken", or "to cease to exist,"[2] a combination of prefix ἐκ- (ek-), from preposition ἐκ (ek), "out," and of verb λείπω (leípō), "to be absent".[3][4]

Umbra, penumbra and antumbra[edit]

Umbra, penumbra and antumbra cast by an opaque object occulting a larger light source.

The region of the Moon's shadow in a solar eclipse is divided into three parts:[5]

  • The umbra, within which the Moon completely covers the Sun (more precisely, its photosphere).
  • The antumbra, extending beyond the tip of the umbra, within which the Moon is completely in front of the Sun but too small to completely cover it.
  • The penumbra, within which the Moon is only partially in front of the Sun.

During a lunar eclipse only the umbra and penumbra are applicable. This is because Earth's apparent diameter from the viewpoint of the Moon is nearly four times that of the Sun.

The first contact occurs when the Moon's disc first starts to impinge on the Sun's; second contact is when the Moon's disc moves completely within the Sun's; third contact when it starts to move out of the Sun's; and fourth or last contact when it finally leaves the Sun's disc entirely.

The same terms may be used analogously in describing other eclipses, e.g., the antumbra of Deimos crossing Mars, or Phobos entering Mars's penumbra.

A total eclipse occurs when the observer is within the umbra, an annular eclipse when the observer is within the antumbra, and a partial eclipse when the observer is within the penumbra.


L\ =\ \frac{r \cdot R_o}{R_s - R_o}


Eclipse cycles[edit]

An eclipse cycle takes place when a series of eclipses are separated by a certain interval of time. This happens when the orbital motions of the bodies form repeating harmonic patterns. A particular instance is the saros, which results in a repetition of a solar or lunar eclipse every 6,585.3 days, or a little over 18 years (because this is not a whole number of days, successive eclipses will be visible from different parts of the world).[7]

Earth–Moon System[edit]

A symbolic orbital diagram from the view of the Earth at the center, with the sun and moon projected upon the celestial sphere, showing the Moon's two nodes where eclipses can occur.

An eclipse involving the Sun, Earth and Moon can occur only when they are nearly in a straight line, allowing one to be hidden behind another, viewed from the third. Because the orbital plane of the Moon is tilted with respect to the orbital plane of the Earth (the ecliptic), eclipses can occur only when the Moon is close to the intersection of these two planes (the nodes). The Sun, Earth and nodes are aligned twice a year (during an eclipse season), and eclipses can occur during a period of about two months around these times. There can be from four to seven eclipses in a calendar year, which repeat according to various eclipse cycles, such as a saros.

Between 1901 and 2100 there are the maximum of seven eclipses in:[8]

  • four (penumbral) lunar and three solar eclipses: 1908, 2038.
  • four solar and three lunar eclipses: 1917, 1973, 2094.
  • five solar and two lunar eclipses: 1934.

Excluding penumbral lunar eclipses, there are a maximum of seven eclipses in:[9]

  • 1591, 1656, 1787, 1805, 1917, 1935, 1982, and 2094.

Solar eclipse[edit]

Main article: Solar eclipse
The progression of a solar eclipse on August 1, 2008, viewed from Novosibirsk, Russia. The time between shots is three minutes.

As observed from the Earth, a solar eclipse occurs when the Moon passes in front of the Sun. The type of solar eclipse event depends on the distance of the Moon from the Earth during the event. A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon's shadow. When the umbra does not reach the surface of the Earth, the Sun is only partially occulted, resulting in an annular eclipse. Partial solar eclipses occur when the viewer is inside the penumbra.[10]



Geometry of a total solar eclipse (not to scale)

During a solar eclipse, the Moon can sometimes perfectly cover the Sun because its size is nearly the same as the Sun's when viewed from the Earth. A total solar eclipse is in fact an occultation while an annular solar eclipse is a transit.

When observed at points in space other than from the Earth's surface, the Sun can be eclipsed by bodies other than the Moon. Two examples include when the crew of Apollo 12 observed the Earth to eclipse the Sun in 1969 and when the Cassini probe observed Saturn to eclipse the Sun in 2006.

Lunar eclipse[edit]

Main article: Lunar eclipse
The progression of a lunar eclipse from right to left. Totality is shown with the first two images. These required a longer exposure time to make the details visible.


There are three types of lunar eclipses: penumbral, when the Moon crosses only the Earth's penumbra; partial, when the Moon crosses partially into the Earth's umbra; and total, when the Moon crosses entirely into the Earth's umbra. Total lunar eclipses pass through all three phases. Even during a total lunar eclipse, however, the Moon is not completely dark. Sunlight refracted through the Earth's atmosphere enters the umbra and provides a faint illumination. Much as in a sunset, the atmosphere tends to more strongly scatter light with shorter wavelengths, so the illumination of the Moon by refracted light has a red hue,[13] thus the phrase 'Blood Moon' is often found in descriptions of such lunar events as far back as eclipses are recorded.[14]

Historical record[edit]

Records of solar eclipses have been kept since ancient times. Eclipse dates can be used for chronological dating of historical records. A Syrian clay tablet, in the Ugaritic language, records a solar eclipse which occurred on March 5, 1223 B.C.,[15] while Paul Griffin argues that a stone in Ireland records an eclipse on November 30, 3340 B.C.[16] Positing classical-era astronomers' use of Babylonian eclipse records mostly from the 13th century BC provides a feasible and mathematically consistent[17] explanation for the Greek finding all three lunar mean motions (synodic, anomalistic, draconitic) to a precision of about one part in a million or better. Chinese historical records of solar eclipses date back over 4,000 years and have been used to measure changes in the Earth's rate of spin.[18]

By the 1600s, European astronomers were publishing books with diagrams explaining how lunar and solar eclipses occurred.[19][20] In order to disseminate this information to a broader audience and decrease fear of the consequences of eclipses, booksellers printed broadsides explaining the event either using the science or via astrology.[21]

Some other planets and Pluto[edit]

Gas giants[edit]

Saturn occults the Sun as seen from the Cassini–Huygens space probe

The gas giant planets (Jupiter,[22] Saturn,[23] Uranus,[24] and Neptune)[25] have many moons and thus frequently display eclipses. The most striking involve Jupiter, which has four large moons and a low axial tilt, making eclipses more frequent as these bodies pass through the shadow of the larger planet. Transits occur with equal frequency. It is common to see the larger moons casting circular shadows upon Jupiter's cloudtops.





Transit of Phobos from Mars, as seen by the Mars Opportunity rover (10 March 2004).

On Mars, only partial solar eclipses (transits) are possible, because neither of its moons is large enough, at their respective orbital radii, to cover the Sun's disc as seen from the surface of the planet. Eclipses of the moons by Mars are not only possible, but commonplace, with hundreds occurring each Earth year. There are also rare occasions when Deimos is eclipsed by Phobos.[28] Martian eclipses have been photographed from both the surface of Mars and from orbit.


Pluto, with its proportionately large moon Charon, is also the site of many eclipses. A series of such mutual eclipses occurred between 1985 and 1990.[29] These daily events led to the first accurate measurements of the physical parameters of both objects.[30]

Mercury and Venus[edit]


Eclipsing binaries[edit]



The first eclipsing binary star system to be discovered was Algol, a star system in the constellation Perseus. Normally this star system has a visual magnitude of 2.1. However, every 2.867 days the magnitude decreases to 3.4 for more than nine hours. This is caused by the passage of the dimmer member of the pair in front of the brighter star.[33] The concept that an eclipsing body caused these luminosity variations was introduced by John Goodricke in 1783.[34]

See also[edit]


  1. ^ Staff (March 31, 1981). "Science Watch: A Really Big Syzygy" (Press release). The New York Times. Retrieved 2008-02-29. 
  2. ^
  3. ^
  4. ^
  5. ^ Espenak, Fred (September 21, 2007). "Glossary of Solar Eclipse Terms". NASA. Retrieved 2008-02-28. 
  6. ^ Green, Robin M. (1985). Spherical Astronomy. Oxford University Press. ISBN 0-521-31779-7. 
  7. ^ Espenak, Fred (July 12, 2007). "Eclipses and the Saros". NASA. Retrieved 2007-12-13. 
  8. ^
  9. ^
  10. ^ Hipschman, R. "Solar Eclipse: Why Eclipses Happen". Retrieved 2008-12-01. 
  11. ^ Zombeck, Martin V. (2006). Handbook of Space Astronomy and Astrophysics (Third ed.). Cambridge University Press. p. 48. ISBN 0-521-78242-2. 
  12. ^ Staff (January 6, 2006). "Solar and Lunar Eclipses". NOAA. Retrieved 2007-05-02. 
  13. ^ Phillips, Tony (February 13, 2008). "Total Lunar Eclipse". NASA. Retrieved 2008-03-03. 
  14. ^ Ancient Timekeepers,
  15. ^ de Jong, T.; van Soldt, W. H. (1989). "The earliest known solar eclipse record redated". Nature 338 (6212): 238–240. Bibcode:1989Natur.338..238D. doi:10.1038/338238a0. Retrieved 2007-05-02. 
  16. ^ Griffin, Paul (2002). "Confirmation of World's Oldest Solar Eclipse Recorded in Stone". The Digital Universe. Retrieved 2007-05-02. 
  17. ^ See DIO 16 p.2 (2009). Though those Greek and perhaps Babylonian astronomers who determined the three previously unsolved lunar motions were spread over more than four centuries (263 BC to 160 AD), the math-indicated early eclipse records are all from a much smaller span: the 13th century BC. The anciently attested Greek technique: use of eclipse cycles, automatically providing integral ratios, which is how all ancient astronomers' lunar motions were expressed. Long-eclipse-cycle-based reconstructions precisely produce all of the 24 digits appearing in the three attested ancient motions just cited: 6247 synod = 6695 anom (System A), 5458 synod = 5923 drac (Hipparchos), 3277 synod = 3512 anom (Planetary Hypotheses). By contrast, the System B motion, 251 synod = 269 anom (Aristarchos?), could have been determined without recourse to remote eclipse data, simply by using a few eclipse-pairs 4267 months apart.
  18. ^ "Solar Eclipses in History and Mythology". Bibliotheca Alexandrina. Retrieved 2007-05-02. 
  19. ^ Girault, Simon (1592). Globe dv monde contenant un bref traite du ciel & de la terra. Langres, France. p. Fol. 8V. 
  20. ^ Hevelius, Johannes (1652). Observatio Eclipseos Solaris Gedani. Danzig, Poland. 
  21. ^ Stephanson, Bruce; Bolt, Marvin; Friedman, Anna Felicity (2000). The Universe Unveiled: Instruments and Images through History. Cambridge, UK: Cambridge University Press. pp. 32–33. ISBN 052179143X. 
  22. ^ "Start eclipse of the Sun by Callisto from the center of Jupiter" (Observed at 00:28 UT). JPL Solar System Simulator. 3 June 2009. Retrieved 2008-06-05. 
  23. ^ "Eclipse of the Sun by Titan from the center of Saturn" (Observed at 02:46 UT). JPL Solar System Simulator. 3 August 2009. Retrieved 2008-06-05. 
  24. ^ "Brief Eclipse of the Sun by Miranda from the center of Uranus" (Observed at 19:58 UT (JPL Horizons S-O-T=0.0565)). JPL Solar System Simulator. 22 January 2007. Retrieved 2008-06-05. 
  25. ^ "Transit of the Sun by Nereid from the center of Neptune" (Observed at 20:19 UT (JPL Horizons S-O-T=0.0079)). JPL Solar System Simulator. 28 March 2006. Retrieved 2008-06-05. 
  26. ^ "Roemer's Hypothesis". MathPages. Retrieved 2007-01-12. 
  27. ^ Cassini, Giovanni D. (1694). "Monsieur Cassini His New and Exact Tables for the Eclipses of the First Satellite of Jupiter, Reduced to the Julian Stile, and Meridian of London". Philosophical Transactions of the Royal Society 18 (207-214): 237–256. doi:10.1098/rstl.1694.0048. JSTOR 102468. Retrieved 2007-04-30. 
  28. ^ Davidson, Norman (1985). Astronomy and the Imagination: A New Approach to Man's Experience of the Stars. Routledge. ISBN 0-7102-0371-3. 
  29. ^ Buie, M. W.; Polk, K. S. (1988). "Polarization of the Pluto-Charon System During a Satellite Eclipse". Bulletin of the American Astronomical Society 20: 806. Bibcode:1988BAAS...20..806B. 
  30. ^ Tholen, D. J.; Buie, M. W.; Binzel, R. P.; Frueh, M. L. (1987). "Improved Orbital and Physical Parameters for the Pluto-Charon System". Science 237 (4814): 512–514. Bibcode:1987Sci...237..512T. doi:10.1126/science.237.4814.512. PMID 17730324. Retrieved 2008-03-11. 
  31. ^ Espenak, Fred (May 29, 2007). "Planetary Transits Across the Sun". NASA. Retrieved 2008-03-11. 
  32. ^ Bruton, Dan. "Eclipsing binary stars". Midnightkite Solutions. Retrieved 2007-05-01. 
  33. ^ Price, Aaron (January 1999). "Variable Star Of The Month: Beta Persei (Algol)". AAVSO. Archived from the original on 2007-04-05. Retrieved 2007-05-01. 
  34. ^ Goodricke, John; Englefield, H. C. (1785). "Observations of a New Variable Star". Philosophical Transactions of the Royal Society of London 75 (0): 153–164. Bibcode:1785RSPT...75..153G. doi:10.1098/rstl.1785.0009. 

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