Goat Kids Asterism Triangulates Near Golden Capella in Auriga

Summary: The three star Goat Kids asterism triangulates near golden Capella, brightest star in Auriga the Charioteer constellation.

Auriga the Charioteer safely cradles Goat Kids (Eta Aurigae, Zeta Aurigae) with his left arm in 1822 depiction by Scottish rhetorician Alexander Jamieson in A Celestial Atlas, Plate IV: Alexander Jamieson, Public Domain, via U.S. Naval Observatory Library

As winter approaches for mid-northern latitudes, the three star Goat Kids asterism triangulates in the northeastern sky near golden Capella, brightest star in Auriga the Charioteer constellation.

The Goat Kids asterism triangulates prominently as three stars lying below Capella (Alpha Aurigae; α Aurigae; Alpha Aur; α Aur). Capella shines as the constellation’s brightest star and as nighttime’s sixth brightest star.

A she-goat snuggles against the charioteer’s left shoulder. Greek astronomer Claudius Ptolemy (ca. 100-ca. 170 CE) identified Capella as representing the she-goat’s body in his second century treatise, originally entitled Mathematical Treatise (Ancient Greek: Μαθηματικὴ Σύνταξις, Mathēmatikē Syntaxis) and now known as Almagest (al-majisṭī, “almagest”: Arabic transliteration of Ancient Greek: μεγίστη, megístē, “greatest”).

The narrow triangle representing the Kids angles noticeably outward from the constellation’s five-sided, or pentagonal, basic outline. The Goat Kids asterism comprises three stars. Epsilon Aurigae, Zeta Aurigae and Eta Aurigae participate in the triangular asterism. Eta Aurigae and Zeta Aurigae represent the asterism’s two goat kids.

Epsilon Aurigae (ε Aurigae; Epsilon Aur; ε Aur) lies southwest of Capella. The mid-third magnitude star shines as the brightest of the Goat Kids asterism’s stellar trio and as Auriga the Charioteer constellation’s fifth brightest star. Epsilon Aurigae rates as nighttime’s 181st brightest star, according to British astrophysicist Richard Powell’s Hipparcos (High Precision Parallax Collecting Satellite) Catalogue-based list of 300 brightest stars.

Ptolemy’s Almagest identifies Epsilon Aurigae as representing the charioteer’s left elbow. Epsilon Aurigae marks the apex of the asterism’s triangle from a distance of around 2,000 light years.

University of Illinois Emeritus Professor of Astronomy James B. “Jim” Kaler describes Epsilon Aurigae as “One of the weirdest and least understood stars in the sky.” Epsilon Aurigae is actually an eclipsing binary star system with an orbital period of 27.1 years. Eclipses by its mysterious companion last for about two years (640 to 730 days).

The star system’s last dimming in the 20th century happened during the 1982 to 1984 eclipse. The first dimming in the 21st century occurred from 2009 to 2011. The star system’s next eclipse in the 21st century is slated to take place from 2036 to 2038.

Epsilon Aurigae is known popularly as Almaaz. Its traditional name derives from al-mācz, the Arabic word for “billy goat.”

Zeta Aurigae (ζ Aurigae; Zeta Aur; ζ Aur) anchors one of the bases of the triangular asterism. The orange supergiant is the dimmest of the Goat Kids asterism’s three stars. Zeta Aurigae participates in the Goat Kids asterism from a distance of around 790 light years.

As with Epsilon Aurigae, the fourth magnitude star is actually an eclipsing binary star system. Every 2.66 years (972.183 days), the orange supergiant eclipses, or hides, its smaller, hot blue class B companion.

Zeta Aurigae is known popularly as Haedus I. Its traditional name derives from the Latin word, haedus, meaning “young goat, kid.”

Zeta Aurigae is also known as Sadatoni. This traditional name derives from an Arabic phrase, as-sācid aθ-θānī, which means “the second arm (of the charioteer).”

Eta Aurigae (η Aur; η Aurigae) anchors the other base of the Goat Kids asterism’s triangle. The blue-white main sequence dwarf is the asterism’s second brightest star. Eta Aurigae holds place number 205 in British astrophysicist Richard Powell’s list of nighttime’s 300 brightest stars.

Eta Aurigae triangulates from a distance of about 220 light years.

Third magnitude star is the Goat Kids asterism’s only single star. Unlike Epsilon Aurigae and Zeta Aurigae, Eta Aurigae offers no evidence of a companion star.

The takeaway for the Goat Kids asterism that triangulates near golden Capella in Auriga the Charioteer is that the trio angles colorfully and noticeably outward in its fortuitous westward location in the northern celestial hemisphere.

Epsilon Aurigae, one of the kids in the Goat Kids asterism, is a mysterious, eclipsing binary star system; depicted by artist concept as a main bright star with a B star companion encircled by a dusty disk; NASA ID PIA12484; image addition date 2010-01-05; image credit NASA/JPL-Caltech: May be used for any purpose without prior permission, via NASA JPL Photojournal

Acknowledgment

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

Image credits:

Auriga the Charioteer safely cradles Goat Kids (Eta Aurigae, Zeta Aurigae) with his left arm in 1822 depiction by Scottish rhetorician Alexander Jamieson in A Celestial Atlas, Plate IV: Alexander Jamieson, Public Domain, via U.S. Naval Observatory Library @ http://aa.usno.navy.mil/library/

Epsilon Aurigae, one of the kids in the Goat Kids asterism, is a mysterious, eclipsing binary star system; depicted by artist concept as a main bright star with a B star companion encircled by a dusty disk; NASA ID PIA12484; image addition date 2010-01-05; image credit NASA/JPL-Caltech: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA12484;
Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA @ https://www.nasa.gov/multimedia/imagegallery/image_feature_1580.html;
Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Video Library @ https://images.nasa.gov/details/PIA12484

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