First Point of Aries for Spring Equinox Actually Happens in Pisces

Summary: The First Point of Aries that is linked with the spring equinox actually happens in Pisces now.

Two annual equinoxes, in spring and in autumn, mark intersections of plane of ecliptic (red) with celestial equator (light blue/white); spring equinox (upper right) occurs with sun in front of Pisces the Fishes constellation: Tau’olunga, CC BY SA 3.0, via Wikimedia Commons

The First Point of Aries, associated with the spring equinox and also known as March equinox point, actually happens in Pisces the Fishes constellation now.

The First Point of Aries derives its name from its anciently marking the location of the sun at the time of the Northern Hemisphere’s vernal (Latin: ver, “spring”) equinox. The point, however, is not permanent.

The process known as precession of the equinoxes explains the moving, or precessing (Latin: praecedere, “to go before”), of the year’s two equinoxes, in spring and in autumn, through the zodiac’s ecliptic coordinate system of 12 signs, or divisions. Each sign of the imaginary zodiacal belt equates to a regular division of 30 degrees of the ecliptic, the sun’s apparent annual path across the imaginary, Earth-centered celestial sphere. The regularity of the divisions results in an inexact correspondence with the irregular boundaries of their 12 namesake constellations.

Motional effects of complex forces, known as perturbations, account for the slow, westward circuit of the ecliptic coordinate system. Completion of one circuit takes about 26,000 years.

The spring and autumnal equinoxes respectively mark the sun’s two crossings of the celestial equator, another imaginary great circle projected from Earth’s equator outward to the imaginary, Earth-centered celestial sphere. The astronomical term obliquity of the ecliptic references Earth’s slanted rotational axis with respect to the perpendicular plane of the Earthly orbit around the sun.

Twice each year, the sun’s apparent path along the ecliptic intersects the celestial equator. The vernal equinox describes the sun’s crossing of the intersection from south to north. The spring passage point is considered an ascending, or north, node, to reflect northward movement.

The ecliptic’s north node continues to be known as the First Point of Aries even though precession has shifted that point westward into Aries the Ram’s neighbor, Pisces the Fishes constellation. The First Point of Aries previously was associated with a point south of Gamma Arietis (γ Arietis; Gamma Ari; γ Ari). The white and gray double star marks the ram’s left horn. It has the traditional name of Mesarthim, a corruption of Arabic for “two of something” (al-sharatan). Mesarthim’s location near the First Point of Aries explains the epithet of “First Star of Aries” for the constellation’s fourth brightest star.

The First Point of Aries presently is sited in Pisces, south of the Great Square of Pegasus. The ascending node of the spring equinox now lies southeast of Lambda Piscium (Lambda Psc; λ Piscium; λ Psc), a bluish white star in the southeastern section of the Circlet of Pisces asterism. The five star Circlet of Pisces asterism is sited in Pisces the Fishes constellation’s western fish.

Belgian celestial mechanics expert Jean Meeus (born Dec. 12, 1928) dates the March equinox’s precession from Aries to Pisces back to 68 BCE. He calculates the next constellatory boundary crossover by the spring equinoctial sun as occurring in 2597. In that year, the sun will be in front of the constellation of Aquarius the Water Bearer.

The takeaway for the First Point of Aries for the spring equinox is the process of the precession of the equinoxes, which very slowly moves the vernal point of intersection of the celestial equator with the ecliptic through the zodiac. Previously happening in Aries the Ram constellation, the First Point of Aries now occurs in Pisces the Fishes.

Graphic shows shifting of point of vernal equinox, known as First Point in Aries, along the ecliptic over 6,000+-year period: Dbachmann, CC BY SA 3.0, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Two annual equinoxes, in spring and in autumn, mark intersections of plane of ecliptic (red) with celestial equator (light blue/white); spring equinox (upper right) occurs with sun in front of Pisces the Fishes constellation: Tau’olunga, CC BY SA 3.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Ecliptic_path.jpg

Graphic shows shifting of point of vernal equinox, known as First Point in Aries, along the ecliptic over 6,000+-year period: Dbachmann, CC BY SA 3.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Equinox_path.png

For further information:

Bakich, Michael E. “The Circlet of Pisces, the Southern Cigar Galaxy, and Elliptical Galaxy NGC 7840.” Astronomy Magazine > Observing > Observing Podcasts. Oct. 17, 2013.
Available @ http://www.astronomy.com/observing/observing-podcasts/2013/10/the-circlet-of-pisces-the-southern-cigar-galaxy-and-ngc-7840

EarthSky. “Moon Near First Point in Aries.” EarthSky > Tonight. Nov. 10, 2016.
Available @ http://earthsky.org/tonight/the-first-point-in-aries

Fisher, Mark. "First Point of Aries." Glyph Web eSky (Electronic Sky) > Concepts.
Available @ ttp://www.glyphweb.com/esky/concepts/firstpointofaries.html

“Fixed Star Mesarthim Arietis.” Constellations of Words > Stars.
Available @ http://www.constellationsofwords.com/stars/Mesarthim.html

Kaler, James B. (Jim). “Western Pisces.” University of Illinois Astronomy Department > Star of the Week.
Available @ http://stars.astro.illinois.edu/sow/psc-w-p.html

McClure, Bruce. “Aries? Here’s Your Constellation.” EarthSky > Constellations. Dec. 1, 2016.
Available @ http://earthsky.org/constellations/aries-heres-your-constellation

McClure, Bruce. “Hamal Is an Ancient Equinox Star.” EarthSky > Brightest Stars. Dec. 1, 2016.
Available @ http://earthsky.org/brightest-stars/hamal-ancient-equinox-star

McClure, Bruce. “Pisces? Here’s Your Constellation.” EarthSky > Constellations. Nov. 2, 2016.
Available @ http://earthsky.org/constellations/pisces-heres-your-constellation

McClure, Bruce; Deborah Byrd. “When Does the Age of Aquarius Begin?” EarthSky > Human World > Science Wire. Jan. 22, 2016.
Available @ http://earthsky.org/human-world/when-will-the-age-of-aquarius-begin

“Mesarthim (Gamma Arietis).” University of Illinois Astronomy Department > Star of the Week.
Available @ http://stars.astro.illinois.edu/sow/mesarthim.html

Ridpath, Ian. “Aries the Ram.” Ian Ridpath > Star Tales.
Available @ http://www.ianridpath.com/startales/aries.htm

“Spring Equinox - Vernal Equinox.” Time And Date > Sun & Moon.
Available @ https://www.timeanddate.com/calendar/spring-equinox.html

Stern, David P. “Precession.” NASA Goddard Space Flight Center (GSFC) International Solar Terrestrial Physics (ISTP) > From Stargazers to Starships. Last updated Sept. 17, 2004.
Available @ http://www-istp.gsfc.nasa.gov/stargaze/Sprecess.htm

“Why Is the Vernal Equinox Called the ‘First Point of Aries’ When the Sun Is Actually in Pisces on This Date?” University of Southern Maine > Southworth Planetarium.
Available @ https://usm.maine.edu/planet/why-vernal-equinox-called-first-point-aries-when-sun-actually-pisces-date

Zimmermann, Kim Ann. “Aries Constellation: Facts About the Ram.” Space.com > Science & Astronomy. Aug. 10, 2012.
Available @ http://www.space.com/17052-aries-constellation.html