View source for Zodiac

{{Short description|Area of the sky divided into twelve signs}}
{{for multi|the East Asian zodiac|Chinese zodiac|other uses|Zodiac (disambiguation)}}
{{Pp-pc}}
{{Use dmy dates|date=February 2021}}
{{Use American English|date=November 2022}}
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 | caption1          = The [[Earth's orbit]] around the [[Sun]] causes the apparent motion of the latter along the [[ecliptic]] (red). Earth is [[axial tilt|axially tilted]] 23.4° relative to this plane; its equator, [[celestial equator|extended to the stars]], is shown in light&nbsp;blue.
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The '''zodiac''' is a belt-shaped region of the sky that extends approximately 8° north and south [[celestial latitude]] of the [[ecliptic]] – the [[Sun path|apparent path]] of the [[Sun]] across the [[celestial sphere]] over the course of the year. Within this zodiac belt appear the [[Moon]] and the brightest [[planet]]s, along their orbital planes.<ref name="oxford-def">{{cite web|title=zodiac|url=https://en.oxforddictionaries.com/definition/zodiac|archive-url=https://web.archive.org/web/20160926223903/https://en.oxforddictionaries.com/definition/zodiac|url-status=dead|archive-date=26 September 2016|website=Oxford Dictionaries|publisher=Oxford University Press|access-date=19 September 2017}}</ref> The zodiac is divided along the ecliptic into 12 equal parts, called "[[astrological sign|signs]]", each occupying 30° of [[celestial longitude]]. These signs roughly correspond to the [[astronomical]] [[constellation]]s with the following modern names:<ref>Because the signs are each 30° in longitude but constellations have irregular shapes, and because of precession, they do not correspond exactly to the boundaries of the [[constellations]] after which they are named.</ref><ref>{{cite journal | last=Noble| first=William| title=Papers communicated to the Association. The Signs of the Zodiac. | journal=Journal of the British Astronomical Association | volume=12 | pages=242–244| bibcode=1902JBAA...12..242N| year=1902}}</ref> [[Aries (astrology)|Aries]], [[Taurus (astrology)|Taurus]], [[Gemini (astrology)|Gemini]], [[Cancer (astrology)|Cancer]], [[Leo (astrology)|Leo]], [[Virgo (astrology)|Virgo]], [[Libra (astrology)|Libra]], [[Scorpio (astrology)|Scorpio]], [[Sagittarius (astrology)|Sagittarius]], [[Capricorn (astrology)|Capricorn]], [[Aquarius (astrology)|Aquarius]], and [[Pisces (astrology)|Pisces]]. 

The signs have been used to determine the time of the year by identifying each sign with the days of the year the Sun is in the respective sign. In [[Western astrology]], and formerly [[astronomy]], the time of each sign is associated with different attributes. The zodiacal system and its angular measurement in 360 [[sexagesimal]] [[Degree (angle)|degree (°)]] originated with [[Babylonian astronomy]] during the [[1st millennium BC]], probably during the [[Achaemenid Empire]]. It was communicated into [[Greek astronomy]] by the 2nd century BC, as well as into developing the [[Hindu astrology|Hindu zodiac]]. Due to the [[precession of the equinoxes]], the time of year that the Sun is in a given constellation has changed since Babylonian times, and the point of [[March equinox]] has moved from [[Aries (constellation)|Aries]] into [[Pisces (constellation)|Pisces]]. 

The zodiac forms a [[celestial coordinate system]], or more specifically an [[ecliptic coordinate system]], which takes the ecliptic as the origin of latitude and the [[position of the Sun|Sun's position]] at [[Equinox (celestial coordinates)|vernal equinox]] as the origin of longitude.<ref>{{cite book |url=https://books.google.com/books?id=z3gRvA2J3DYC&pg=PA94 |title=A Compleat System of Astronomy |first=Charles |last=Leadbetter |year=1742 |publisher=J. Wilcox, London |page=94}}; numerous examples of this notation appear throughout the book.</ref> In modern astronomy, the ecliptic coordinate system is still used for tracking Solar System objects.

==<span class="anchor" id="Etymology"></span><span class="anchor" id="Names"></span>Name==
The English word ''{{linktext|zodiac}}'' derives from {{wikt-lang|la|zōdiacus}},<ref>{{cite book | title=A Concise Etymological Dictionary of the English Language | page=622 | first=Walter William | last=Skeat | author-link=Walter William Skeat | date=1924 | publisher=Clarendon Press | url=https://books.google.com/books?id=QkfWAAAAMAAJ&pg=PA622 | access-date=20 March 2023 | archive-date=7 April 2023 | archive-url=https://web.archive.org/web/20230407151842/https://books.google.com/books?id=QkfWAAAAMAAJ&pg=PA622 | url-status=live }}</ref> the [[Latinisation of names|Latinized]] form of the [[Ancient Greek language|Ancient Greek]] {{transliteration|grc|zōdiakòs}} ({{wikt-lang|grc|ζῳδιακός}}),<ref>{{cite encyclopedia
 | last1=Hübner | first1=Wolfgang | last2=Hunger | first2=Hermann
 | title=Zodiac | isbn=9789004122598
 | encyclopedia=Brill’s New Pauly | doi=10.1163/1574-9347_bnp_e1213810 }}</ref> meaning "of or relating to little animals", {{transliteration|grc|Zōdion}} ({{wikt-lang|grc|ζῴδιον}}) being the diminutive of {{transliteration|grc|zōon}} ({{wikt-lang|grc|ζῷον}}, "animal").<ref>{{OEtymD|zodiac|accessdate=2023-03-06}}</ref> The name reflects the prominence of animals (and [[mythological hybrid]]s) among the twelve signs. In English, the term "zodiac" may also be used in reference to or translation for the similar twelve year cycle (also sometimes applied to other time units than years) of the East Asian-derived systems referred to as the [[Chinese zodiac]] (see also, [[Earthly Branches]]): similarities include the use of animal or theriomorphic figures associated with a twelve year cycle used culturally to allege or describe personality traits, life events, and their interrelationships—thus this use in translation.{{cn|date=May 2025}}

== Usage ==
[[File:Zodiac (PSF).png|thumb|Modern zodiac wheel showing the 12 signs used in [[horoscopic astrology]]]]
The zodiac was in use by the [[Roman era]], based on concepts inherited by [[Hellenistic astronomy]] from [[Babylonian astronomy]] of the [[Neo-Babylonian|Chaldean period]] (mid-1st millennium BC), which, in turn, derived from an earlier system of lists of stars along the ecliptic.<ref>See [[MUL.APIN]]. See also {{cite book|last1=Lankford|first1=John|last2=Rothenberg|first2=Marc|title=History of Astronomy: An Encyclopedia|url=https://books.google.com/books?id=berWESi5c5QC&pg=RA1-PA43|year=1997|publisher=Taylor & Francis|isbn=978-0-8153-0322-0|page=43}}</ref> The construction of the zodiac is described in [[Ptolemy]]'s comprehensive 2nd century AD work, the ''[[Almagest]]''.<ref>{{Cite book | last1=Ptolemy | given1=Claudius | author-link=Ptolemy | title=The Almagest | publisher=Princeton University Press | place=Princeton, New Jersey | date=1998 | isbn=0-691-00260-6}} Translated and annotated by [[G. J. Toomer]]; with a foreword by [[Owen Gingerich]].</ref>

Although the zodiac remains the basis of the [[ecliptic coordinate system]] in use in [[astronomy]] besides the [[equatorial coordinate system|equatorial]] one,<ref>{{cite web | last=Shapiro | first=Lee T. | url=http://spaceplace.nasa.gov/starfinder3/ | title=Constellations in the zodiac | publisher=[[NASA]] | access-date=27 April 2011 | archive-date=4 March 2012 | archive-url=https://web.archive.org/web/20120304212807/http://spaceplace.nasa.gov/starfinder3 | url-status=live }}</ref><ref>{{cite book | title=Finding Our Place in the Solar System: The Scientific Story of the Copernican Revolution | first1=Todd | last1=Timberlake | first2=Paul | last2=Wallace | date=28 March 2019 | page=33 | isbn=9781107182295 | publisher=Cambridge University Press | url=https://books.google.com/books?id=wFqHDwAAQBAJ&pg=PA33 | access-date=20 March 2023 | archive-date=7 April 2023 | archive-url=https://web.archive.org/web/20230407062433/https://books.google.com/books?id=wFqHDwAAQBAJ&pg=PA33 | url-status=live }}</ref> the term and the names of the twelve signs are today mostly associated with [[horoscopic astrology]].<ref>{{cite journal | first=B. L. | last=van der Waerden | author-link=Bartel Leendert van der Waerden | title=History of the zodiac | journal=Archiv für Orientforschung | volume=16 | date=1953 | pages=216–230 | bibcode=1953ArOri..16..216V }}</ref> The term "zodiac" may also refer to the region of the [[celestial sphere]] encompassing the paths of the planets corresponding to the band of about 8 arc degrees above and below the ecliptic. The zodiac of a given planet is the band that contains the path of that particular body; e.g., the "zodiac of the Moon" is the band of 5° above and below the ecliptic. By extension, the "zodiac of the comets" may refer to the band encompassing most [[short-period comet]]s.<ref>[[OED]], citing [[John Harris (writer)|J. Harris]], ''[[Lexicon Technicum]]'' (1704): "Zodiack of the Comets, [[Giovanni Domenico Cassini|Cassini]] hath observed a certain Tract [...] within whose Bounds [...] he hath found most Comets [...] to keep."</ref>

== History ==
{{further|Former constellation}}

=== Early history ===
As early as the 14th century BC a complete list of the 36 Egyptian [[decan]]s was placed among the hieroglyphs adorning the tomb of [[Seti I]]; they figured again in the temple of [[Ramesses II]], and characterize every Egyptian astrological monument. Both the famous zodiacs of [[Dendera]] display their symbols, identified by [[Karl Richard Lepsius]].<ref>{{EB1911 |wstitle=Zodiac |volume=28 |page=997 |first=Agnes Mary |last=Clerke |author-link=Agnes Mary Clerke|inline=1}}</ref>

[[File:Antoninus Pius Drachm showing a Zodiac wheel.jpg|thumb|400px|Roman Egyptian coin of [[Antoninus Pius]] (dated year 8 of his reign or 145 AD) showing his portrait and a Zodiac wheel with the busts of [[Helios]] and [[Selene]] in the center]]
[[File:Beit alfa01.jpg|thumb|A sixth-century mosaic zodiac wheel in synagogue [[Beth Alpha]] incorporating Greek-Byzantine elements, Israel]]
[[File:F4.v. zodiac circle with planets - NLW MS 735C.png|thumb|Zodiac circle with planets, {{circa|1000}} – ''NLW MS 735C'']]

The division of the ecliptic into the zodiacal signs originates in [[Babylonian astronomy]] during the first half of the [[1st millennium BC]]. The zodiac draws on stars in earlier [[Babylonian star catalogues]], such as the [[MUL.APIN]] catalogue, which was compiled around 1000 BC. Some constellations can be traced even further back, to Bronze Age ([[Old Babylonian Empire]]) sources, including [[Gemini (constellation)|Gemini]] "The Twins", from {{langx|sux|𒀯𒈦𒋰𒁀𒃲𒃲|translit=<sup>MUL</sup>MAŠ.TAB.BA.GAL.GAL}} "The Great Twins"; [[Cancer (constellation)|Cancer]] "The Crab", from {{langx|sux|𒀯𒀠𒇻|translit=<sup>MUL</sup>AL.LUL}} "The Crayfish", among others.<ref name=Rogers_1998/><ref>{{cite book
 | chapter=History of the Sumerian, Accadian, Assyrian, and West Semitic calendars
 | title=Babylonian menologies and the Semitic calendars
 | first=S. | last=Langdon | author-link=Stephen Herbert Langdon | year=1935
 | series=The Schweich Lectures of the British Academy, 1933
 | publisher=Oxford University Press | publication-place=London
 | url=https://gospelstudies.org.uk/biblicalarchaeology/pdf/schweich-lectures/1933_babylonian-menogies_langdon.pdf
 | access-date=2024-01-15 }}</ref>

Around the end of the fifth century BC, [[Babylonia]]n astronomers divided the ecliptic into 12 equal "signs", by analogy to 12 schematic months of 30 days each. Each sign contained 30° of [[celestial longitude]], thus creating the first known celestial coordinate system. According to calculations by modern astrophysics, the zodiac was introduced between 409 and 398 BC, during [[Achaemenid Empire|Persian rule]],<ref>{{cite book
 | last=Ossendrijver
 | first=Mathieu
 | date=2013
 | chapter=Science, Mesopotamian
 | title=The Encyclopedia of Ancient History
 | doi=10.1002/9781444338386.wbeah21289
 | isbn=9781405179355
 | chapter-url=https://amor.cms.hu-berlin.de/~ossendrm/encyc-ancient-hist-2013-ossendrijver.pdf
 | access-date=2022-04-18
 | archive-date=16 June 2022
 | archive-url=https://web.archive.org/web/20220616052542/https://amor.cms.hu-berlin.de/~ossendrm/encyc-ancient-hist-2013-ossendrijver.pdf
 | url-status=live
 }}</ref> and probably within a very few years of 401 BC.<ref>{{Cite journal | last=Britton | first=John P. | date=2010 | title=Studies in Babylonian lunar theory: part III. The introduction of the uniform zodiac | journal=Archive for History of Exact Sciences | volume=64 | issue=6 | pages=617–663 | jstor=41134332 | doi=10.1007/S00407-010-0064-Z | s2cid=122004678 | quote=[T]he zodiac was introduced between −408 and −397 and probably within a very few years of −400.}}</ref> Unlike modern astrologers, who place the beginning of the sign of [[Aries (astrology)|Aries]] at the position of the Sun at the [[Equinox (celestial coordinates)|vernal equinox]] in the [[Northern Hemisphere]] ([[March equinox]]), Babylonian astronomers fixed the zodiac in relation to stars, placing the beginning of [[Cancer (astrology)|Cancer]] at the "Rear Twin Star" ([[Pollux (star)|β Geminorum]]) and the beginning of [[Aquarius (astrology)|Aquarius]] at the "Rear Star of the Goat-Fish" ([[Delta Capricorni|δ Capricorni]]).<ref>{{cite book | last=Steele | first=John M. | date=2012 | orig-year=2008 | title=A Brief Introduction to Astronomy in the Middle East | publisher=Saqi | place=London | edition=electronic | isbn=9780863568961 }}</ref>

Due to the [[precession of the equinoxes]], the time of year the Sun is in a given constellation has changed since Babylonian times, as the point of March equinox has moved from [[Aries (constellation)|Aries]] into [[Pisces (constellation)|Pisces]].<ref>{{Cite web | last=Plait | first=Phil | date=26 September 2016 | title=No, NASA hasn't changed the zodiac signs or added a new one | website=Bad Astronomy | url=http://www.slate.com/blogs/bad_astronomy/2016/09/26/no_nasa_didn_t_change_your_astrological_sign.html | access-date=2 October 2016 | archive-date=2 October 2016 | archive-url=https://web.archive.org/web/20161002070120/http://www.slate.com/blogs/bad_astronomy/2016/09/26/no_nasa_didn_t_change_your_astrological_sign.html | url-status=live }}</ref>

Because the divisions were made into equal arcs of 30° each, they constituted an ideal system of reference for making predictions about a planet's longitude. However, Babylonian techniques of observational measurements were in a rudimentary stage of evolution.<ref name=Sachs/> They measured the position of a planet in reference to a set of "normal stars" close to the ecliptic (±9° of latitude). The normal stars were used as observational reference points to help position a planet within this ecliptic coordinate system.<ref>{{cite book | last=Aaboe | first=Asger H. | author-link=Asger Aaboe | title=Episodes from the Early History of Astronomy | place=New York | publisher=Springer | date=2001 | pages=37–38 | isbn=9780387951362 }}</ref>

In [[Babylonian astronomical diaries]], a planet position was generally given with respect to a zodiacal sign alone, though less often in specific degrees within a sign.<ref name="Rochberg">{{cite journal | last=Rochberg | first=Francesca | author-link=Francesca Rochberg | date=1988 | title=Babylonian Horoscopes | journal=Transactions of the American Philosophical Society | volume=88 | issue=1 | pages=i–164 | jstor=1006632 | doi=10.2307/1006632 | publisher=American Philosophical Society }}</ref> When the degrees of longitude were given, they were expressed with reference to the 30° of the zodiacal sign, i.e., not with a reference to the continuous 360° ecliptic.<ref name="Rochberg" /> In astronomical [[ephemerides]], the positions of significant astronomical phenomena were computed in [[sexagesimal]] fractions of a degree (equivalent to [[Minute and second of arc|minutes and seconds of arc]]).<ref>{{cite book | last=Aaboe | first=Asger H. | author-link=Asger Aaboe | title=Episodes from the Early History of Astronomy | place=New York | publisher=Springer | date=2001 | pages=41–45 | isbn=9780387951362 }}</ref> For daily ephemerides, the daily positions of a planet were not as important as the astrologically significant dates when the planet crossed from one zodiacal sign to the next.<ref name="Rochberg" />

=== Hebrew astronomy and astrology ===
Knowledge of the Babylonian zodiac is said to be reflected in the [[Hebrew Bible]]; [[E. W. Bullinger]] interpreted the creatures that appear in the [[book of Ezekiel]] ([[Ezekiel 1#Verse 10|1:10]]) as the middle signs of the four quarters of the zodiac,<ref>Bullinger, E.W. ''The Witness of the Stars''</ref><ref>Kennedy, D. James. ''The Real Meaning of the Zodiac''.</ref>{{Better source needed|date=January 2024}} with the Lion as [[Leo (astrology)|Leo]], the Bull as [[Taurus (astrology)|Taurus]], the Man as Aquarius and the Eagle as a higher aspect of Scorpio.<ref>{{Cite book | first=Richard Hinckley | last=Allen | year=1963 | pages=213–215 | title=Star names - Their Lore and Meaning | publisher=Dover Books | publication-place=New York }} argued for ''Scorpio'' having previously been called ''Eagle''. for Scorpio.</ref> Some authors have linked the signs of the zodiac with the [[twelve tribes of Israel]], and with the lunar [[Hebrew calendar]], which has twelve [[lunar months]] in a [[lunar year]]. [[Ernest L. Martin|Ernest L. Martin]] and others have argued that the arrangement of the tribes around the [[Tabernacle]] (reported in the [[Book of Numbers]]) corresponded to the order of the zodiac, with [[Tribe of Judah|Judah]], [[Tribe of Reuben|Reuben]], [[Tribe of Ephraim|Ephraim]], and [[Tribe of Dan|Dan]] representing the middle signs of Leo, Aquarius, Taurus, and Scorpio, respectively. Such connections were taken up by [[Thomas Mann]], who in his novel ''[[Joseph and His Brothers]]'', attributes characteristics of a sign of the zodiac to each tribe, in his rendition of the [[Blessing of Jacob]].{{citation needed|date=September 2017}}

=== Hellenistic and Roman era ===
[[File:Dendera.jpg|thumb|left|The 1st century BC [[Dendera zodiac]] (19th-century engraving)]]
The Babylonian star catalogs entered [[Greek astronomy]] in the 4th century BC, via [[Eudoxus of Cnidus]].<ref name=Rogers_1998/>
Babylonia or [[Chaldea]] in the Hellenistic world came to be so identified with astrology that "Chaldean wisdom" became among [[Greeks]] and [[Ancient Rome|Romans]] the synonym of [[divination]] through the [[planets]] and [[star]]s. [[Hellenistic astrology]] derived in part from Babylonian and [[Ancient Egyptian astronomy|Egyptian astrology]].<ref>{{cite thesis | url=http://www.astrologer.com/aanet/pub/transit/jan2005/babylonian.htm | last=Powell | first=Robert | title=Influence of Babylonian Astronomy on the Subsequent Defining of the Zodiac | year=2004 | degree=PhD | archive-url=https://web.archive.org/web/20090521081306/http://www.astrologer.com/aanet/pub/transit/jan2005/babylonian.htm | archive-date=21 May 2009 }} summarized by anonymous editor.</ref> [[Horoscopic astrology]] first appeared in [[Ptolemaic Kingdom|Ptolemaic Egypt]] (305 BC–30 BC). The [[Dendera zodiac]], a relief dating to {{circa|50 BC}}, is the first known depiction of the classical zodiac of twelve signs.{{cn|date=May 2025}}

The earliest extant Greek text using the Babylonian division of the zodiac into 12 signs of 30 equal degrees each is the ''Anaphoricus'' of [[Hypsicles of Alexandria]] (fl.{{nbsp}}190{{nbsp}}BC).<ref>{{ Cite book | last=Montelle | first=Clemency |author-link=Clemency Montelle | editor-last=Steele | editor-first=John M. | date=2016 | title=The Circulation of Astronomical Knowledge in the Ancient World | chapter=The ''Anaphoricus'' of Hypsicles of Alexandria | pages=287–315 | series=Time, Astronomy, and Calendars: Texts and Studies | volume=6 | publisher=Brill | location=Leiden | isbn=978-90-0431561-7 }}</ref> Particularly important in the development of Western horoscopic astrology was the astrologer and astronomer [[Tetrabiblos|Ptolemy]], whose work ''Tetrabiblos'' laid the basis of the [[Western astrological tradition]].<ref>{{cite book | last=Saliba | first=George | author-link=George Saliba | year=1994 | title=A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam |location=New York | publisher=New York University Press | page=67 | isbn=978-0-8147-8023-7 }}.</ref> Under the Greeks, and Ptolemy in particular, the planets, Houses, and signs of the zodiac were rationalized and their function set down in a way that has changed little to the present day.<ref>{{cite book |last1=Parker |first1=Julia |first2=Derek |last2=Parker |year=1990 |title=The New Compleat Astrologer|isbn=978-0517697009 |publisher=Crescent Books |location=New York, NY|page=16 }}</ref> Ptolemy lived in the 2nd century AD, three centuries after the discovery of the [[precession]] of the equinoxes by [[Hipparchus]] around 130 BC. Hipparchus's lost work on precession never circulated very widely until it was brought to prominence by Ptolemy,<ref name="Springer">{{cite book|last1=Graßhoff|first1=Gerd|title=The History of Ptolemy's Star Catalogue|date=1990|publisher=Springer|isbn=9780387971810|page=73}}</ref> and there are few explanations of precession outside the work of Ptolemy until late Antiquity, by which time Ptolemy's influence was widely established.<ref name=Geminos>{{cite book|last1=Evans|first1=James|last2=Berggren|first2=J. Lennart|title=Geminos's Introduction to the Phenomena|date=2006|publisher=Princeton University Press|isbn=069112339X|page=113}}</ref> Ptolemy clearly explained the theoretical basis of the western zodiac as being a [[tropical astrology|tropical coordinate system]], by which the zodiac is aligned to the equinoxes and solstices, rather than the visible constellations that bear the same names as the zodiac signs.<ref name="Ptolemy's Tetrabiblos">{{cite book|last1=Ashmand|first1=J. M.|title=Ptolemy's Tetrabiblos|publisher=Astrology Classics|page=37 (I.XXV)|year=2011|isbn=978-1461118251}}</ref>

=== Hindu zodiac ===

According to mathematician-historian [[Jean-Étienne Montucla|Montucla]], the Hindu zodiac was adopted from the [[Ancient Greek astronomy|Greek zodiac]] through communications between ancient India and the Greek empire of [[Bactria]].<ref name="Mill1817">{{cite book | first=James | last=Mill | author-link=James Mill | title=The History of British India | url=https://books.google.com/books?id=KQAMAAAAYAAJ&pg=PA402 | year=1817 | publisher=Baldwin, Cradock, and Joy | page=409}}</ref> The [[Hindu zodiac]] uses the [[Sidereal astrology|sidereal coordinate system]], which makes reference to the fixed stars. The tropical zodiac (of Mesopotamian origin) is divided by the intersections of the [[ecliptic]] and [[equator]], which shifts in relation to the backdrop of fixed stars at a rate of 1° every 72 years, creating the phenomenon known as precession of the equinoxes. The Hindu zodiac, being sidereal, does not maintain this seasonal alignment, but there are still similarities between the two systems. The Hindu zodiac signs and corresponding Greek signs sound very different, being in Sanskrit and Greek respectively, but their symbols are nearly identical.<ref name="Schmidt">{{cite web |last1=Schmidt |first1=Robert H. |title=The Relation of Hellenistic to Indian Astrology |url=http://www.projecthindsight.com/articles/vedic.html |publisher=Project Hindsight |access-date=4 July 2016 |archive-date=3 July 2016 |archive-url=https://web.archive.org/web/20160703034617/http://www.projecthindsight.com/articles/vedic.html |url-status=live }}</ref> For example, ''dhanu'' means "bow" and corresponds to Sagittarius, the "archer", and ''kumbha'' means "water-pitcher" and corresponds to Aquarius, the "water-carrier".<ref name="Dalal2010">{{cite book |last=Dalal |first=Roshen |title=Hinduism: An Alphabetical Guide |url=https://books.google.com/books?id=DH0vmD8ghdMC&pg=PA89 |year=2010 |publisher=Penguin Books India |isbn=978-0-14-341421-6 |page=89 |access-date=20 October 2016 |archive-date=7 March 2023 |archive-url=https://web.archive.org/web/20230307164318/https://books.google.com/books?id=DH0vmD8ghdMC&pg=PA89 |url-status=live }}</ref>

=== Middle Ages ===
[[File:Angers Cathedral South Rose Window of Christ with Zodiac.jpg|thumb|Angers Cathedral South Rose Window of Christ (center) with elders (bottom half) and zodiac (top half). Medieval stained glass by Andre Robin after the fire of 1451]]

During the [[Abbasid Caliphate|Abbasid era]], Greek reference books were translated into [[Arabic]], and [[Astronomy in the medieval Islamic world|Islamic astronomers]] then did their own observations, correcting Ptolemy's Almagest. One such book was [[Abd al-Rahman al-Sufi|Al-Sufi]]'s ''[[Book of Fixed Stars]]'', which has pictorial depictions of 48 constellations. The book was divided into three sections: constellations of the zodiac, constellations north of the zodiac, and southern constellations. When Al-Sufi's book, and other works, were translated in the 11th century, there were mistakes made in the translations. As a result, some stars ended up with the names of the constellation they belong to (e.g. [[Hamal]] in Aries).

The High Middle Ages saw a revival of interest in [[Greco-Roman magic]], first in [[Kabbalism]] and later continued in [[Renaissance magic]]. This included magical uses of the zodiac, as found, e.g., in the [[Sefer Raziel HaMalakh]].

The zodiac is found in medieval [[stained glass]] as at [[Angers Cathedral]], where the master glass maker, André Robin, made the ornate [[rosette window|rosettes]] for the North and South transepts after the fire there in 1451.<ref>King, David. '[http://vidimus.org/issues/issue-48/feature/ Angers Cathedral] {{Webarchive|url=https://web.archive.org/web/20131217215830/http://vidimus.org/issues/issue-48/feature/ |date=17 December 2013 }}', (book review of Karine Boulanger's 2010 book, ''Les Vitraux de la Cathédrale d'Angers'', the 11th volume of the ''Corpus Vitrearum'' series from France), ''Vitemus:  the only on-line magazine devoted to medieval stained glass'', Issue 48, February 2011, retrieved 17 December 2013.</ref>

=== Medieval Islamic era ===
[[File:Ottoman Sundial at the Debbane Palace museum.jpg|alt=Circular brass time measurement device with engraved Arabic toponyms and zodiac symbols.|thumb|Ottoman-style sundial with folded gnomon and compass. The sundial features engraved toponyms in Arabic and zodiac symbols. [[Debbane Palace]] museum, [[Lebanon]]]]

[[Astrology]] emerged in the 8th century AD as a distinct discipline in Islam,<ref name="ayduz">{{cite book |last1=Ayduz |first1=Salim |title=The Oxford Encyclopedia of Philosophy, Science, and Technology in Islam |date=2014 |publisher=Oxford University Press}}</ref>{{rp|64}} with a mix of Indian, Hellenistic Iranian and other traditions blended with Greek and Islamic astronomical knowledge, for example Ptolemy's work and Al-Sufi's Book of Fixed Stars. A knowledge of the influence that the stars have on events on the earth was important in Islamic civilization. As a rule, it was believed that the signs of the zodiac and the planets control the destiny not only of people but also of nations, and that the zodiac has the ability to determine a person's physical characteristics as well as intelligence and personal traits.<ref>{{cite book |last1=Andalusi |first1=Salem |title=Science in the medical world: 'Book of the categories of nations |date=1991 |publisher=University of Texas Press |location=Austin |page=XXV}}</ref>

The practice of astrology at this time could be divided into four broader categories: [[Natal astrology|Genethlialogy]], Catarchic Astrology, Interrogational Astrology and General Astrology.<ref name="ayduz"/>{{rp|65}} However the most common type of astrology was Genethlialogy, which examined all aspects of a person's life in relation to the planetary positions at their birth; more commonly known as our horoscope.<ref name="ayduz"/>{{rp|65}}

Astrology services were offered widely across the empire, mainly in bazaars, where people could pay for a reading.<ref name="sardar">{{cite web |last1=Sardar |first1=Marika |title=Astronomy and Astrology in the Medieval Islamic World |url=https://www.metmuseum.org/toah/hd/astr/hd_astr.htm |website=Met Museum |date=August 2011 |access-date=19 October 2020 |archive-date=23 October 2020 |archive-url=https://web.archive.org/web/20201023010719/http://www.metmuseum.org/toah/hd/astr/hd_astr.htm |url-status=live }}</ref> Astrology was valued in the royal courts, for example, the Abbasid Caliph Al-Mansur used astrology to determine the best date for founding the new capital of Baghdad.<ref name="ayduz"/>{{rp|66}} While horoscopes were generally widely accepted by society, many scholars condemned the use of astrology and divination, linking it to occult influences.<ref>{{cite book |last1=Varisco |first1=Daniel Martin|editor1-last=Selin |editor1-first=Helaine |editor-link=Helaine Selin |title=Astronomy Across Cultures: The History of Non-Western Astrology |date=2000 |publisher=Springer Science+Business Media Dordrecht |isbn=978-94-010-5820-9 |page=617}}</ref> Many theologians and scholars thought that it went against the tenets of Islam; as only God should be able to determine events rather than astrologers looking at the positions of the planets.<ref name="sardar"/>

In order to calculate someone's horoscope, an astrologer would use three tools: an astrolabe, ephemeris and a takht. First, the astrologer would use an astrolabe to find the position of the sun, align the rule with the persons time of birth and then align the rete to establish the altitude of the sun on that date.<ref>{{cite journal |last1=Winterburn |first1=Emily |title=Using an Astrolabe |journal=Foundation for Science Technology and Civilisation |date=August 2005 |pages=7 |url=https://www.academia.edu/2301156 |access-date=30 July 2022 |archive-date=28 February 2023 |archive-url=https://web.archive.org/web/20230228135159/https://www.academia.edu/2301156 |url-status=live }}</ref>  Next, the astrologer would use an ephemeris, a table denoting the mean position of the planets and stars within the sky at any given time.<ref name="saliba">{{cite journal |last1=Saliba |first1=George |title=The Role of the Astrologer in Medieval Islamic Society |journal=Bulletin d'études orientales |date=1992 |volume=44 |page=50 |jstor=41608345 |url=https://www.jstor.org/stable/41608345 |access-date=19 October 2020 |archive-date=20 October 2020 |archive-url=https://web.archive.org/web/20201020185136/https://www.jstor.org/stable/41608345 |url-status=live }}</ref> Finally, the astrologer would add the altitude of the sun taken from the astrolabe, with the mean position of the planets on the person's birthday, and add them together on the takht (also known as the dustboard).<ref name="saliba"/> The dust board was merely a tablet covered in sand; on which the calculations could be made and erased easily.<ref name="sardar"/> Once this had been calculated, the astrologer was then able to interpret the horoscope. Most of these interpretations were based on the zodiac in literature. For example, there were several manuals on how to interpret each zodiac sign, the treatise relating to each individual sign and what the characteristics of these zodiacs were.<ref name="sardar"/>

=== Early modern ===

An example of the use of signs as astronomical coordinates may be found in the ''Nautical Almanac and Astronomical Ephemeris for the year 1767''. The "Longitude of the Sun" columns show the sign (represented as a digit from 0 to and including 11), degrees from 0 to 29, minutes, and seconds.<ref>''[https://archive.org/details/nauticalalmanac07offigoog Nautical Almanac and Astronomical Ephemeris for the year 1767]''. London: Board of Longitude, 1766.</ref>

[[Mughal Empire|Mughal king]] [[Jahangir]] issued an attractive series of coins in gold and silver depicting the twelve signs of the zodiac.<ref>{{cite web
 | title=Jahangir's 12 gold coins of the Zodiac, Mughal Empire, ca. 1620 A.D.
 | publisher=University of Washington Libraries, Special Collections
 | year=1972
 | url=https://digitalcollections.lib.washington.edu/digital/collection/ic/id/7341/
 | access-date=2023-05-17
 | archive-date=17 May 2023
 | archive-url=https://web.archive.org/web/20230517165358/https://digitalcollections.lib.washington.edu/digital/collection/ic/id/7341/
 | url-status=live
 }}</ref>

<gallery mode=packed heights=200>
File:P.9 a volvella of the moon. A volvella is a moveable device for working out the position of the sun and moon in the zodiac.jpg|A volvella of the moon. A volvella is a moveable device for working out the position of the Sun and Moon in the zodiac, 15th century
File:Monasterio de Svetitskhoveli, Miskheta, Georgia, 2016-09-29, DD 41.jpg|17th-century fresco of [[Christ]] in the zodiac circle, [[Svetitskhoveli|Cathedral of Living Pillar]], [[Georgia (country)|Georgia]] 
</gallery>

== Twelve signs ==
{{Main|Astrological sign}}

What follows is a list of the signs of the modern zodiac (with the ecliptic longitudes of their first points), where 0° Aries is understood as the vernal equinox, with their Latin, Greek, Sanskrit, and Babylonian names. But the Sanskrit and the name equivalents (after c.500 BC) denote the constellations only, not the tropical zodiac signs. The "English translation" is not usually used by English speakers. The Latin names are standard English usage (except that "Capricorn" is used rather than "Capricornus").
{|class="wikitable"
|-
! [[House (astrology)|House]] !!  [[Universal Character Set characters|Unicode Character]] !! [[Ecliptic|Ecliptic Longitude<br>(''a'' ≤ {{math|''λ''}} < ''b'')]] !! Latin name !![[Gloss (annotation)|Gloss]] !! Greek name ([[Romanization of Greek]]) !![[Hindu zodiac|Sanskrit name]] !! [[Babylonian zodiac|Sumero-Babylonian name]]<ref>[[MUL.APIN]]; Peter Whitfield, ''History of Astrology'' (2001); W. Muss-Arnolt, ''The Names of the Assyro-Babylonian Months and Their Regents'', Journal of Biblical Literature (1892).</ref>
|-
|1 ||♈︎︎||  0°|| [[Aries (astrology)|Aries]] ||[[sheep|Ram]]||{{lang|grc|Κριός}} (''Krios'')|| {{IAST|Meṣa}} ({{lang|sa|मेष}})||{{lang|sux-Latn|<sup>MUL</sup> LU.ḪUN.GA}}<ref>{{Cite web|url=http://oracc.iaas.upenn.edu/ccpo/cbd/qpn/qpn.x0000076.html|title=ccpo/qpn/Agru[1]|website=oracc.iaas.upenn.edu|access-date=2 September 2019|archive-date=2 September 2019|archive-url=https://web.archive.org/web/20190902115314/http://oracc.iaas.upenn.edu/ccpo/cbd/qpn/qpn.x0000076.html|url-status=live}}</ref>  "Agrarian Worker", [[Dumuzid the Shepherd|Dumuzi]]
|-
|2||♉︎︎||  30°||[[Taurus (astrology)|Taurus]] ||[[Bull]]||{{lang|grc|Ταῦρος}} (''Tauros'')|| {{IAST|Vṛṣabha}} ({{lang|sa|वृषभ}})||{{lang|sux-Latn|<sup>MUL</sup>GU<sub>4</sub>.AN.NA}} "Divine [[Bull of Heaven]]"
|-
|3||♊︎︎||  60°||[[Gemini (astrology)|Gemini]] ||[[Twin]]s||{{lang|grc|Δίδυμοι}} (''Didymoi'')|| {{IAST|Mithuna}} ({{lang|sa|मिथुन}})|| {{lang|sux-Latn|<sup>MUL</sup>MAŠ.TAB.BA.GAL.GAL}} "[[Lugal-irra and Meslamta-ea|Great Twins]]"
|-
|4||♋︎︎||  90°||[[Cancer (astrology)|Cancer]] ||[[Crab]]||{{lang|grc|Καρκίνος}} (''Karkinos'')||  {{IAST|Karka}} ({{lang|sa|कर्क}})||{{lang|sux-Latn|<sup>MUL</sup>AL.LUL}}  "[[Crayfish]]"
|-
|5||♌︎︎||  120°|| [[Leo (astrology)|Leo]] ||[[Lion]]||{{lang|grc|Λέων}} (''Leōn'')|| {{IAST|Siṃha}} ({{lang|sa|सिंह}})||{{lang|sux-Latn|<sup>MUL</sup>UR.GU.LA}} "[[Lion]]"
|-
|6||♍︎︎||  150°|| [[Virgo (astrology)|Virgo]] ||[[Maiden]]||{{lang|grc|Παρθένος}} (''Parthenos'')|| {{IAST|Kanyā}} ({{lang|sa|कन्या}})||{{lang|sux-Latn|<sup>MUL</sup>AB.SIN}} "The Furrow"* *"The goddess [[Shala]]'s ear of grain"
|-
|7||♎︎︎||  180°|| [[Libra (astrology)|Libra]] ||[[Weighing scale|Scales]]||{{lang|grc|Ζυγός}} (''Zygos'')|| {{IAST|Tulā}} (तुला)||{{lang|sux-Latn|<sup>MUL</sup>ZIB.BA.AN.NA}} "Scales"
|-
|8||♏︎︎||  210°|| [[Scorpio (astrology)|Scorpio]] ||[[Scorpion]]||{{lang|grc|Σκoρπίος}} (''Skorpios'')<ref>Alternative form: {{lang|grc|Σκορπίων}} ''Skorpiōn''. Later form (with [[synizesis]]): {{lang|el|Σκορπιός}}.</ref> || {{IAST|Vṛścika}} ({{lang|sa|वृश्चिक}})|| 	{{lang|sux-Latn|<sup>MUL</sup>GIR.TAB}}  "[[Scorpion]]"
|-
|9||♐︎︎||  240°|| [[Sagittarius (astrology)|Sagittarius]] || ([[Centaur]]) [[archery|Archer]]||{{lang|grc|Τοξότης}} (''Toxotēs'')|| {{IAST|Dhanuṣa}} ({{lang|sa|धनु}}ष)||{{lang|sux-Latn|<sup>MUL</sup>[[Pabilsag|PA.BIL.SAG]]}}, ''[[Bitu (god)|Nedu]]'' "[[soldier]]"
|-
|10||♑︎︎||  270°|| [[Capricorn (astrology)|Capricorn]] || [[Mountain goat|Mountain Goat]] or [[Goat-Horned]] / [[Sea goat|Sea-Goat]]||{{lang|grc|Αἰγόκερως}} (''Aigokerōs'')|| {{IAST|Makara}} ({{lang|sa|मकर}})||{{lang|sux-Latn|<sup>MUL</sup>SUḪUR.MAŠ}} "[[Sea goat|Goat-Fish]]" of [[Enki]]
|-
|11||♒︎︎||  300°|| [[Aquarius (astrology)|Aquarius]] ||[[Pitcher (container)|Water-Bearer]]||{{lang|grc|Ὑδροχόος}} (''Hydrokhoos'')|| {{IAST|Kumbha}} ({{lang|sa|कुंभ}})|| {{lang|sux-Latn|<sup>MUL</sup>GU.LA}} "Great One" (i.e. [[Enki]]), later ''{{lang|akk-Latn|qâ}}'' "pitcher"
|-
|12||♓︎︎||  330°|| [[Pisces (astrology)|Pisces]] || 2 [[Fish]]<ref>''American Heritage Dictionary of the English Language'' 3rd ed., s.v. "Pisces."</ref>||{{lang|grc|Ἰχθύες}} (''Ikhthyes'')|| {{IAST|Mīna}} ({{lang|sa|मीन}})||{{lang|sux-Latn|<sup>MUL</sup>SIM.MAḪ}}  "Tail of the Swallow"; DU.NU.NU "fish-cord"
|}

These twelve signs have been arranged into a nursery rhyme as a mnemonic device:<ref>{{cite journal
 | title=The Apparent Motions of the Planets
 | last=Aitken | first=R. G. | author-link=Robert Grant Aitken
 | journal=Astronomical Society of the Pacific Leaflets
 | volume=3 | issue=131 | page=238 | year=1940
 | bibcode=1940ASPL....3..238A }}</ref>

{{Poem quote|
The ram, the bull, the heavenly twins,
And next the crab, the lion shines,
    The virgin and the scales,
The scorpion, archer, and the goat,
The man who holds the watering-pot,
    And fish with glittering scales.
| sign=[[Isaac Watts]]
}}
Another mnemonic is ''A Tense Gray Cat Lay Very Low, Sneaking Slowly, Contemplating A Pounce''.<ref>{{cite journal | first=Meghan | last=Jones | url=http://rd.com/list/mnemonic-devices-to-remember-anything | title=15 Mnemonic Devices That'll Help You Remember Just About Anything | journal=Reader's Digest | date=23 December 2022 | access-date=2025-01-26 | archive-date=22 September 2023 | archive-url=https://web.archive.org/web/20230922174731/https://www.rd.com/list/mnemonic-devices-to-remember-anything/ | url-status=dead }}</ref><ref>{{cite book | first=James M. | last=Russell | url=https://books.google.com/books?id=bFluDwAAQBAJ&pg=PT41 | title=Never Eat Shredded Wheat: Weird Ways to Remember Things | publisher=Michael O'Mara Books | date=18 October 2018 | isbn=978-1-78243-991-2 }}</ref>

The following table compares the [[Gregorian calendar|Gregorian]] dates on which the Sun enters a sign in the Ptolemaic [[tropical astrology|tropical]] zodiac, and a sign in two [[sidereal astrology|sidereal]] systems: one proposed by [[Cyril Fagan]], and a fourteen-sign system proposed by Steven Schmidt which adds [[Ophiuchus]] (see below) and [[Cetus (constellation)|Cetus]] (the [[International Astronomical Union|IAU]] boundaries of which just graze by the ecliptic):
[[File:Zodiac German Woodcut.jpg|thumb|The zodiac signs in a 16th-century woodcut]]
The beginning of Aries is defined as the moment of [[March equinox|vernal equinox]], and all other dates shift accordingly.<ref>{{Cite web|title="Why is the vernal equinox called the "First Point of Aries" when the Sun is actually in Pisces on this date?"|publisher=University of Southern Maine|url=https://usm.maine.edu/planet/why-vernal-equinox-called-first-point-aries-when-sun-actually-pisces-date|access-date=9 February 2021|archive-date=4 February 2021|archive-url=https://web.archive.org/web/20210204071744/https://usm.maine.edu/planet/why-vernal-equinox-called-first-point-aries-when-sun-actually-pisces-date|url-status=live}}</ref>
The precise Gregorian times and dates vary slightly from year to year as the [[Gregorian calendar]] shifts relative to the [[tropical year]]. These variations remain within less than two days' difference in the recent past and the near-future, vernal equinox in [[Universal Time|UT]] always falling either on 20 or 21 March in the period of 1797 to 2043, falling on 19 March in 1796 the last time and in 2044 the next. The vernal equinox has fallen on 20 March UT since 2008, and will continue to do so until 2043.<ref>See {{cite web | url=http://www.ns1763.ca/equinox/eqindex.html | first=Jean | last=Meeus | title=Astronomical Tables of the Sun, Moon, and Planets | year=1983 | publisher=Willmann-Bell, Inc. | location=Richmond, Virginia | archive-url=https://web.archive.org/web/20090409073139/http://www.ns1763.ca/equinox/eqindex.html | archive-date=9 April 2009 }} The date in other time zones may vary.</ref>

[[File:F3.v. Southern hemisphere constellations - NLW MS 735C.png|thumb|290px|Depiction of the southern hemisphere constellations in an 11th-century French manuscript (from the [[Limoges]] area, probably in the milieu of [[Adémar de Chabannes]], fl. 1020&ndash;1034)]]

{{Sidereal and tropical zodiac dates}}

As each sign takes up exactly 30 degrees of the zodiac, the average duration of the solar stay in each sign is one twelfth of a [[sidereal year]], or  30.43 standard [[day]]s. Due to Earth's slight [[orbital eccentricity]], the duration of each sign varies appreciably, between about 29.4 days for Capricorn and about 31.4 days for Cancer (see [[Equation of time]]). In addition, because the Earth's axis is at an angle, some signs take longer to rise than others, and the farther away from the equator the observer is situated, the greater the difference. Thus, signs are spoken of as [[Ascendant|"long" or "short" ascension]].<ref>{{cite book | last=Parker | first=Julia | year=2010 | title=The Astrologer's Handbook | publisher=Alva Press | location=NJ | page=10 | isbn=978-0916360597 }}</ref>

== Constellations ==
{{multiple image
|image1=Constellations ecliptic equirectangular plot.svg
|image2=A Mercator map of the starry heavens (William Croswell, 1810).jpg
|direction=vertical
|width=420
|footer=These two maps of the constellations, made two centuries apart, both show the zodiac constellations along a curved line representing the [[ecliptic]].
}}
[[File:Ophiuchus.jpg|thumb|upright=1.1|18th-century [[star chart]] illustrating the feet of [[Ophiuchus]] crossing the ecliptic]]

In [[Sidereal and tropical astrology|tropical astrology]], the [[astrological sign|zodiacal signs]] are distinct from the [[constellation]]s associated with them, not only because of their drifting apart due to the precession of equinoxes but because the physical constellations take up varying widths of the ecliptic, so the Sun is not in each constellation for the same amount of time.<ref name=EdwardJ>{{cite book|last=James|first=Edward W.|title=Philosophy of science and the occult|date=1982|publisher=State University of New York Press|location=Albany|isbn=0873955722|editor=Patrick Grim}}</ref>{{rp|25}} Thus, [[Virgo (constellation)|Virgo]] takes up 5 times as much [[ecliptic longitude]] as [[Scorpius (constellation)|Scorpius]]. The zodiacal signs are an abstraction from the physical constellations, and each represent exactly {{frac|1|12}}th of the full circle, but the time spent by the Sun in each sign varies slightly due to the eccentricity of the [[Earth's orbit]].

[[Sidereal and tropical astrology|Sidereal astrology]] assigns the zodiac sign approximately to the corresponding constellation. This alignment needs recalibrating every so often to keep the alignment in place.

The ecliptic intersects with 13 constellations of [[Ptolemy]]'s ''[[Almagest]]'',<ref>{{cite book | last1=Peters | first1=Christian Heinrich Friedrich | author1-link=Christian Heinrich Friedrich Peters | first2=Edward Ball | last2=Knobel | author2-link=Edward Knobel | url=http://hbar.phys.msu.ru/gorm/almagest/Peters.htm | title=Ptolemy's Catalogue of Stars: a revision of the Almagest] | publisher=Carnegie Institution of Washington | year=1915 | access-date=19 June 2006 | archive-date=29 August 2013 | archive-url=https://web.archive.org/web/20130829023007/http://hbar.phys.msu.ru/gorm/almagest/Peters.htm | url-status=dead }}
{{cite book |last=Ptolemy |title=Almagest |orig-year=2nd cent. |date=1982 |editor=R. Catesby Taliaferro |page=239 |chapter=VII.5}} Ptolemy refers to the constellation as ''Septentarius'' "the serpent holder".</ref> as well as of the more precisely delineated [[IAU designated constellations]]. In addition to the twelve constellations after which the twelve zodiac signs are named, the ecliptic intersects [[Ophiuchus]],<ref name=Tatum2010>{{cite journal | title=The Signs and Constellations of the Zodiac | last=Tatum | first=Jeremy B. | journal=Journal of the Royal Society of Canada | volume=104 | issue=3 | page=103 | date=June 2010 | bibcode=2010JRASC.104..103T }}</ref> the bottom part of which interjects between Scorpius and Sagittarius. Occasionally this difference between the astronomical constellations and the [[astrological sign]]s is mistakenly reported in the popular press as a "change" to the list of traditional signs by some astronomical body like the IAU, [[NASA]], or the [[Royal Astronomical Society]]. This happened in a 1995 report of the ''[[BBC Nine O'Clock News]]'' and various reports in 2011 and 2016.<ref>{{cite journal |author=Kollerstrom, N. |title=Ophiuchus and the media |journal=The Observatory |date=October 1995 |volume=115 |pages=261–262 |publisher=KNUDSEN; OBS |bibcode=1995Obs...115..261K}}</ref><ref>The notion received further international media attention in January 2011, when it was reported that astronomer Parke Kunkle, a board-member of the Minnesota Planetarium Society, had suggested that Ophiuchus was the zodiac's "13th sign". He later issued a statement to say he had not reported that the zodiac ought to include 13 signs instead of 12, but was only mentioning that there were 13 constellations; reported in ''Mad Astronomy'': [http://io9.com/5733004/your-zodiac-sign-may-have-changed-this-week "Why did your zodiac sign change?"] {{Webarchive|url=https://web.archive.org/web/20110625093016/http://io9.com/5733004/your-zodiac-sign-may-have-changed-this-week |date=25 June 2011 }} 13 January 2011.</ref><ref>{{Cite news |url=http://www.slate.com/blogs/bad_astronomy/2016/09/26/no_nasa_didn_t_change_your_astrological_sign.html |title=No, NASA Didn't Change Your Astrological Sign |first=Phil |last=Plait |newspaper=Slate Magazine |date=26 September 2016 |author-link=Phil Plait |access-date=2 October 2016 |archive-date=2 October 2016 |archive-url=https://web.archive.org/web/20161002070120/http://www.slate.com/blogs/bad_astronomy/2016/09/26/no_nasa_didn_t_change_your_astrological_sign.html |url-status=live }}</ref>

Some "parazodiacal" constellations are touched by the paths of the planets, leading to counts of up to 25 "constellations of the zodiac".<ref name=mosley>{{cite web |url=http://www.ips-planetarium.org/?page=a_mosley1999b |publisher=International Planetarium Society |date=2011 |first=John |last=Mosley |title=The Real, Real Constellations of the Zodiac |access-date=21 March 2017 |archive-date=1 July 2017 |archive-url=https://web.archive.org/web/20170701021831/http://www.ips-planetarium.org/?page=a_mosley1999b |url-status=live }}</ref> The ancient Babylonian [[MUL.APIN]] catalog lists [[Orion (constellation)|Orion]], [[Perseus (constellation)|Perseus]], [[Auriga (constellation)|Auriga]], and [[Andromeda (constellation)|Andromeda]]. Modern astronomers have noted that planets pass through [[Crater (constellation)|Crater]], [[Sextans]], [[Cetus (constellation)|Cetus]], [[Pegasus (constellation)|Pegasus]], [[Corvus (constellation)|Corvus]], [[Hydra (constellation)|Hydra]], [[Orion (constellation)|Orion]], and [[Scutum (constellation)|Scutum]], with [[Venus]] very rarely passing through [[Aquila (constellation)|Aquila]], [[Canis Minor]], [[Auriga (constellation)|Auriga]], and [[Serpens]].<ref name=mosley />

Some other constellations are mythologically associated with the zodiacal ones: [[Piscis Austrinus]], The Southern Fish, is attached to Aquarius. In classical maps, it swallows the stream poured out of Aquarius's pitcher, but perhaps it formerly just swam in it. [[Aquila (constellation)|Aquila]], The Eagle, was possibly associated with the zodiac by virtue of its main star, [[Altair]]. [[Hydra (constellation)|Hydra]] in the Early Bronze Age marked the [[celestial equator]] and was associated with Leo, which is shown standing on the serpent on the [[Dendera zodiac]].<ref name=Rogers_1998>{{cite journal
 | title=Origins of the ancient constellations: I. The Mesopotamian traditions
 | last=Rogers | first=J. H.
 | journal=Journal of the British Astronomical Association
 | volume=108 | issue=1 | pages=9–28
 | date=February 1998 | bibcode=1998JBAA..108....9R
}}<br>{{cite journal
 | title=Origins of the ancient constellations: II. The Mediterranean traditions
 | last=Rogers | first=J. H.
 | journal=Journal of the British Astronomical Association
 | volume=108 | issue=2 | pages=79–89
 | date=April 1998 | bibcode=1998JBAA..108...79R
}}</ref>

{| class="wikitable" style="text-align:left"
|-
! Name
! 1977 [[International Astronomical Union|IAU]] boundaries<ref name=Shapiro>[http://www.ips-planetarium.org/?page=a_shapiro1977 The Real Constellations of the Zodiac.] {{Webarchive|url=https://web.archive.org/web/20160328090559/http://www.ips-planetarium.org/?page=a_shapiro1977 |date=28 March 2016 }} Lee T. Shapiro, director of Morehead Planetarium University of North Carolina (Spring 1977)</ref> (approximate)
! Solar stay<ref name=Shapiro/>
! Brightest star
|-
| [[Aries (constellation)|Aries]]
| {{Zodiac date IAU|0}}
| 25 days
| [[Alpha Arietis|Hamal]]
|-
| [[Taurus (constellation)|Taurus]]
| {{Zodiac date IAU|1}}
| 37 days
| [[Aldebaran]]
|-
| [[Gemini (constellation)|Gemini]]
| {{Zodiac date IAU|2}}
| 31 days
| [[Pollux (star)|Pollux]]
|-
| [[Cancer (constellation)|Cancer]]
| {{Zodiac date IAU|3}}
| 20 days
| [[Beta Cancri|Tarf]]
|-
| [[Leo (constellation)|Leo]]
| {{Zodiac date IAU|4}}
| 37 days
| [[Regulus]]
|-
| [[Virgo (constellation)|Virgo]]
| {{Zodiac date IAU|5}}
| 45 days
| [[Spica]]
|-
| [[Libra (constellation)|Libra]]
| {{Zodiac date IAU|6}}
| 23 days
| [[Beta Librae|Zubeneschamali]]
|-
| [[Scorpius (constellation)|Scorpius]]
| {{Zodiac date IAU|7}}
| 7 days
| [[Antares]]
|-
| [[Ophiuchus (constellation)|Ophiuchus]]
| {{Zodiac date IAU|8}}
| 18 days
| [[Alpha Ophiuchi|Rasalhague]]
|-
| [[Sagittarius (constellation)|Sagittarius]]
| {{Zodiac date IAU|9}}
| 32 days
| [[Epsilon Sagittarii|Kaus Australis]]
|-
| [[Capricornus (constellation)|Capricornus]]
| {{Zodiac date IAU|10}}
| 28 days
| [[Delta Capricorni|Deneb Algedi]]
|-
| [[Aquarius (constellation)|Aquarius]]
| {{Zodiac date IAU|11}}
| 24 days
| [[Beta Aquarii|Sadalsuud]]
|-
| [[Pisces (constellation)|Pisces]]
| {{Zodiac date IAU|12}}
| 38 days
| [[Eta Piscium|Alpherg]]
|}

== Precession of the equinoxes ==
{{Further|Axial precession|Epoch (astronomy)|Sidereal and tropical astrology|Astrological age|Ayanamsa}}
[[File:Equinox path.png|thumb|upright=1.36|Path taken by the point of the [[March equinox]] along the ecliptic over the past 6,000 years]]

The zodiac system was developed in [[Neo-Babylonian|Babylonia]], some 2,500 years ago, during the "[[Age of Aries]]".<ref name=Sachs>{{cite journal | last=Sachs | first=A. | author-link=Abraham Sachs | title=A Classification of the Babylonian Astronomical Tablets of the Seleucid Period | journal=Journal of Cuneiform Studies | publisher=University of Chicago Press | volume=2 | issue=4 | year=1948 | jstor=3515929| doi=10.2307/3515929 | pages=271–290| s2cid=164038422 }}</ref> At the time, it is assumed, the precession of the equinoxes was unknown. Contemporary use of the coordinate system is presented with the choice of interpreting the system either as [[sidereal astrology|sidereal]], with the signs fixed to the [[Fixed stars|stellar background]], or as [[tropical astrology|tropical]], with the signs fixed to the point ([[Euclidean vector|vector]] of the Sun) at the [[March equinox]].<ref name="Rochberg"/>

[[Western astrology]] takes the tropical approach, whereas [[Hindu astrology]] takes the sidereal one. This results in the originally unified zodiacal coordinate system drifting apart gradually, with a clockwise (westward) precession of 1.4 degrees per century.

For the tropical zodiac used in Western astronomy and astrology, this means that the tropical ''sign'' of Aries currently lies somewhere within the ''constellation'' Pisces ("[[Age of Pisces]]").

The sidereal coordinate system takes into account the [[ayanamsa]], ''ayan'' meaning "transit" or "movement", and ''amsa'' meaning 'small part', i.e. movement of equinoxes in small parts. It is unclear when Indians became aware of the precession of the equinoxes, but [[Bhāskara II]]'s 12th-century treatise ''[[Siddhanta Shiromani]]'' gives equations for measurement of precession of equinoxes, and says his equations are based on some lost equations of ''[[Suryasiddhanta]]'' plus the equation of Munjaala.{{cn|date=February 2025}}

The discovery of precession is attributed to Hipparchus around 130 BC. Ptolemy quotes from Hipparchus's now-lost work entitled "On the Displacement of the Solstitial and Equinoctial Points" in the seventh book of his 2nd century astronomical text, ''Almagest'', where he describes the phenomenon of precession and estimates its value.<ref name="Springer"/> Ptolemy clarified that the convention of Greek mathematical astronomy was to commence the zodiac from the point of the vernal equinox and to always refer to this point as "the first degree" of Aries.<ref name=Geminos2>{{cite book|last1=Evans|first1=James|last2=Berggren|first2=J. Lennart|title=Geminos's Introduction to the Phenomena|date=2006|publisher=Princeton University Press|isbn=069112339X|page=115}}</ref> This is known as the "tropical zodiac" (from the Greek word trópos, turn)<ref>{{cite web|title=tropo-|url=http://dictionary.reference.com/browse/tropo-|website=Dictionary.com|publisher=Random House, Inc.|access-date=21 May 2015|archive-date=2 March 2015|archive-url=https://web.archive.org/web/20150302034306/http://dictionary.reference.com/browse/tropo-|url-status=live}}</ref> because its starting point revolves through the circle of background constellations over time.

The principle of the vernal point acting as the first degree of the zodiac for Greek astronomers is described in the 1st century BC astronomical text of [[Geminus]] of Rhodes. Geminus explains that Greek astronomers of his era associate the first degrees of the zodiac signs with the two solstices and the two equinoxes, in contrast to the older Chaldean (Babylonian) system, which placed these points within the zodiac signs.<ref name=Geminos2/> This illustrates that Ptolemy merely clarified the convention of Greek astronomers and did not originate the principle of the tropical zodiac, as is sometimes assumed.

Ptolemy demonstrates that the principle of the tropical zodiac was well known to his predecessors within his astrological text, the ''[[Tetrabiblos]]'', where he explains why it would be an error to associate the regularly spaced signs of the seasonally aligned zodiac with the irregular boundaries of the visible constellations:

{{blockquote|The beginnings of the signs, and likewise those of the terms, are to be taken from the equinoctial and tropical points. This rule is not only clearly stated by writers on the subject, but is especially evident by the demonstration constantly afforded, that their natures, influences and familiarities have no other origin than from the tropics and equinoxes, as has been already plainly shown. And, if other beginnings were allowed, it would either be necessary to exclude the natures of the signs from the theory of prognostication, or impossible to avoid error in then retaining and making use of them; as the regularity of their spaces and distances, upon which their influence depends, would then be invaded and broken in upon.<ref name="Ptolemy's Tetrabiblos"/>}}

== In modern astronomy ==
[[File:Night Sky from Hawai‘i and Chile (iotw2225c).jpg|right|thumb|upright=2|Two false dawns,<ref>{{cite web|title=False Dawn|url=http://www.eso.org/public/images/potw1707a/|website=www.eso.org|access-date=14 February 2017}}</ref> [[gegenschein]] (middle) and the rest of the zodiacal band of the [[zodiacal light]], with the zodiac marked (visually crossed by the [[Milky Way]]), in this composite image of the night sky above the northern and southern hemisphere]]
Astronomically, the zodiac defines a belt of space extending 8°<ref>{{cite journal | title=The Zodiac | last=Holmes | first=Charles Nevers | journal=Popular Astronomy | volume=22 | pages=547–550 | date=November 1914 | bibcode=1914PA.....22..547H }}</ref> or 9° in celestial latitude to the north and south of the [[ecliptic]], within which the orbits of the Moon and the principal planets remain.<ref name="Encyclopædia Britannica">{{cite web|author=Encyclopædia Britannica|title=Zodiac|url=http://www.britannica.com/EBchecked/topic/657680/zodiac|website=Encyclopædia Britannica Online|access-date=7 May 2015|archive-date=2 May 2015|archive-url=https://web.archive.org/web/20150502230613/http://www.britannica.com/EBchecked/topic/657680/zodiac|url-status=live}}</ref> It is a feature of the ecliptic coordinate system – a [[celestial coordinate system]] centered upon the ecliptic (the plane of the Earth's orbit and the Sun's apparent path), by which [[celestial longitude]] is measured in degrees east of the vernal equinox (the ascending intersection of the ecliptic and equator).<ref>{{cite web|author=Encyclopædia Britannica|title=Ecliptic|url=http://www.britannica.com/EBchecked/topic/178159/ecliptic|website=Encyclopædia Britannica Online|access-date=7 May 2015|archive-date=28 April 2015|archive-url=https://web.archive.org/web/20150428114741/http://www.britannica.com/EBchecked/topic/178159/ecliptic|url-status=live}}</ref> The zodiac is narrow in angular terms because most of the Sun's planets have orbits that have only a slight [[Orbital inclination|inclination]] to the [[Orbital plane (astronomy)|orbital plane]] of the Earth.<ref>{{cite web | title=Zodiac | work=Cosmos | publisher=Swinburne University of Technology | url=https://astronomy.swin.edu.au/cosmos/Z/Zodiac | accessdate=2021-05-31 | archive-date=3 August 2021 | archive-url=https://web.archive.org/web/20210803201018/https://astronomy.swin.edu.au/cosmos/Z/Zodiac | url-status=live }}</ref> Stars within the zodiac are subject to [[occultation]]s by the Moon and other Solar System bodies. These events can be useful, for example, to estimate the cross-sectional dimensions of a [[minor planet]], or check a star for a close companion.<ref>{{cite web | url=https://occultations.org/ | access-date=6 March 2018 | title=International Occultation Timing Association | date=18 December 2017 | archive-date=13 March 2018 | archive-url=https://web.archive.org/web/20180313142744/http://occultations.org/ | url-status=live }}</ref>

[[File:Zodiacal Light Seen from Paranal.jpg|right|thumb|Zodiacal light viewed from [[Cerro Paranal]]]]
The Sun's placement upon the vernal equinox, which occurs annually around 21 March, defines the starting point for measurement, the first degree of which is historically known as the "[[First Point of Aries|first point of Aries]]". The first 30° along the ecliptic is nominally designated as the zodiac sign Aries, which no longer falls within the proximity of the constellation Aries since the effect of precession is to move the vernal point through the backdrop of visible constellations. It is currently located near the end of the constellation Pisces, having been within that constellation since the 2nd century AD.<ref name="britannica.com">{{cite web|author=Encyclopædia Britannica|title=Astronomical map|url=http://www.britannica.com/EBchecked/topic/40018/astronomical-map/52787/The-ecliptic-system|website=Encyclopædia Britannica Online|access-date=7 May 2015|archive-date=18 May 2015|archive-url=https://web.archive.org/web/20150518065355/http://www.britannica.com/EBchecked/topic/40018/astronomical-map/52787/The-ecliptic-system|url-status=live}}</ref> The subsequent 30° of the ecliptic is nominally designated the zodiac sign Taurus, and so on through the twelve signs of the zodiac so that each occupies {{frac|1|12}}th (30°) of the zodiac's great circle. Zodiac signs have never been used to determine the boundaries of astronomical constellations that lie in the vicinity of the zodiac, which are, and always have been, irregular in their size and shape.<ref name="Encyclopædia Britannica"/>

The convention of measuring celestial longitude within individual signs was still being used in the mid-19th century,<ref>{{cite book|author=G. Rubie|title=The British Celestial Atlas: Being a Complete Guide to the Attainment of a Practical Knowledge of the Heavenly Bodies|url=https://archive.org/details/britishcelestia00rubigoog|year=1830|publisher=Baldwin & Cradock|page=[https://archive.org/details/britishcelestia00rubigoog/page/n95 79]|quote=The Longitude of a Celestial Object is reckoned on the Ecliptic, in signs and degrees, eastward from the first point of Aries.}}</ref> but modern astronomy now numbers degrees of celestial longitude continuously from 0° to 360°, rather than 0° to 30° within each sign.<ref>{{cite book|title=The Astronomical Almanac for the Year 2017 | publisher=U.S. Government Publishing Office | location=Washington D.C. | date=October 2015 | isbn=978-0-7077-41666 | pages=C6–C21}}</ref> This coordinate system is  primary used by astronomers for observations of Solar System objects.<ref>{{cite book | title=Observing Projects Using Starry Night Enthusiast | first1=Alan T. | last1=Clark | first2=William J. F. | last2=Wilson | first3=Marcel | last3=Bergman | first4=William J. | last4=Kaufmann | first5=Neil F. | last5=Comins | display-authors=1 | page=42 | publisher=W. H. Freeman | date=2008 | edition=eighth | isbn=978-1-4292-1866-5 | url=https://books.google.com/books?id=OHCggyFCjZ0C&pg=PA42 | access-date=20 March 2023 | archive-date=7 April 2023 | archive-url=https://web.archive.org/web/20230407062434/https://books.google.com/books?id=OHCggyFCjZ0C&pg=PA42 | url-status=live }}</ref>

The use of the zodiac as a means to determine astronomical measurement remained the main method for defining celestial positions by Western astronomers until the Renaissance, at which time preference moved to the equatorial coordinate system, which measures astronomical positions by [[right ascension]] and [[declination]] rather than the ecliptic-based definitions of celestial longitude and [[celestial latitude]]. The orientation of equatorial coordinates are aligned with the Earth's axis of rotation, rather than the plane of the planet's orbit around the Sun.<ref name="britannica.com"/>

The word "zodiac" is used in reference to the [[zodiacal cloud]] of dust grains that move among the planets, and the [[zodiacal light]] that originates from their scattering of sunlight.<ref>{{cite journal | title=Unveiling the Milky Way: A New Technique for Determining the Optical Color and Luminosity of Our Galaxy | last1=Licquia | first1=Timothy C. | last2=Newman | first2=Jeffrey A. | last3=Brinchmann | first3=Jarle | journal=The Astrophysical Journal | volume=809 | issue=1 | id=96 | pages=19 | date=August 2015 | doi=10.1088/0004-637X/809/1/96 | arxiv=1508.04446 | bibcode=2015ApJ...809...96L | s2cid=118455273 }}</ref> While its name is derived from the zodiac, the zodiacal light covers the entire night sky, with enhancements in certain directions.<ref>{{cite book | title=Observing Comets, Asteroids, Meteors, and the Zodiacal Light | first1=Stephen J. | last1=Edberg | author1-link=Stephen J. Edberg | first2=David H. | last2=Levy | date=6 October 1994 | page=151 | isbn=9780521420037 | publisher=Cambridge University Press | url=https://books.google.com/books?id=jTPkq1CHlIQC&pg=PA151 | access-date=20 March 2023 | archive-date=7 April 2023 | archive-url=https://web.archive.org/web/20230407151842/https://books.google.com/books?id=jTPkq1CHlIQC&pg=PA151 | url-status=live }}</ref>

==Unicode characters==
In Unicode, the symbols of zodiac signs are encoded in block "Miscellaneous Symbols". They can be forced to look like text by appending U+FE0E, or like emojis by appending U+FE0F:<ref name="Unicode Standard">{{cite web|title=Zodiacal symbols in Unicode block Miscellaneous Symbols|url=https://www.unicode.org/charts/PDF/U2600.pdf#search=Zodiacal|work=The Unicode Standard|date=2010|access-date=23 March 2018|archive-date=22 August 2017|archive-url=https://web.archive.org/web/20170822052003/http://unicode.org/charts/PDF/U2600.pdf#search=Zodiacal|url-status=live}}</ref>
{| class=wikitable
! Unicode character || text || emoji
|-
|{{unichar|2648|aries|html=}} ||♈︎ ||♈️
|-
|{{unichar|2649|taurus|html=}} ||♉︎ ||♉️
|-
|{{unichar|264a|gemini|html=}} ||♊︎ ||♊️
|-
|{{unichar|264b|cancer|html=}} ||♋︎ ||♋️
|-
|{{unichar|264c|leo|html=}} ||♌︎ ||♌️
|-
|{{unichar|264d|virgo|html=}} ||♍︎ ||♍️
|-
|{{unichar|264e|libra|html=}} ||♎︎ ||♎️
|-
|{{unichar|264f|scorpius|html=}} ||♏︎ ||♏️
|-
|{{unichar|2650|sagittarius|html=}} ||♐︎ ||♐️
|-
|{{unichar|2651|capricorn|html=}} ||♑︎ ||♑️
|-
|{{unichar|2652|aquarius|html=}} ||♒︎ ||♒️
|-
|{{unichar|2653|pisces|html=}} ||♓︎ ||♓️
|-
|{{unichar|26ce|ophiuchus|html=}} ||⛎︎ ||⛎️
|}

== See also ==
{{Portal|Astronomy
}}
<!-- alphabetical order please [[WP:SEEALSO]] -->
<!-- please add a short description [[WP:SEEALSO]], via {{subst:AnnotatedListOfLinks}} or {{Annotated link}} -->
{{div col|colwidth=20em|small=yes}}
* {{Annotated link |Astronomical symbols}}
* {{Annotated link |Chinese zodiac}}
* {{Annotated link |Circle of stars}}
* {{Annotated link |Cusp (astrology)}}
* {{Annotated link |Elements of the zodiac}}
* {{Annotated link |History of astrology}}
* {{Annotated link |Jewish astrology}}
* {{Annotated link |Mazzaroth}}
{{div col end}}
<!-- alphabetical order please [[WP:SEEALSO]] -->

== References ==
{{Reflist}}

{{sfn whitelist|CITEREFSchmidt1970}}

== External links ==
{{Commons and category|Zodiac|Zodiac}}
* [https://www.loc.gov/item/2008401701 "A Treatise on Zodiacal Signs and Constellations: Unique Jewels on the Benefits of Keeping Time"] – a manuscript that dates back to 1831 with a focus on Arabic, Coptic and Syriac calendars.

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