Hevelius Introduced Sextans the Sextant Constellation in 1687

Summary: Hevelius introduced Sextans the Sextant constellation in 1687 as a "fiery" group of 12 stars between two constellatory "fiery" animals, Leo and Hydra.

(center) Sextans the Sextant constellation nestles between constellations Leo the Lion and Hydra the Water Snake; 17th-century Polish astronomer Johannes Hevelius named his constellatory astronomical instrument Sextans Uraniae (Urania's Sextant) after ancient Greek goddess Urania (Ancient Greek: Οὐρανία, Ouranía), who, among Greek mythology's nine inspirational Muses (Ancient Greek: Μοῦσαι, Moûsai), was honored as the muse of astronomy; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. VV: Public Domain, via ETH-Bibliothek e-rara

Seventeenth-century Polish astronomer Johannes Hevelius introduced Sextans the Sextant constellation in 1687 as a "fiery" astronomical instrument comprising 12 stars in the space between two constellatory "fiery" animals, Leo the Lion and Hydra the Water Snake.

Johannes Hevelius (Polish: Jan Heweliusz; Jan. 28, 1611-Jan. 28, 1687) presented Uraniae Sextantem (Urania's sextant) as one of 10 constellations that he had visualized in Prodromus Astronomiae. The three-volume astronomical compendium comprised the Prodromus; a star catalogue, Catalogus Stellarum Fixarum; and a star atlas, Firmamentum Sobiescianum sive Uranographia. The catalogue and star atlas, which had been printed in 1687, were left unpublished and the Prodromus was left unfinished by Hevelius's death in that year. The astronomer-selenographer's wife, Polish astronomer Elisabeth Catherina Koopmann Hevelius (Polish: Elżbieta Koopman Heweliusz; Jan. 17, 1647–Dec. 22, 1693), finished the Prodromus and published all three volumes, under her husband's posthumous authorship, in 1690.

Hevelius introduced Uraniae Sextantem, known modernly as Sextans the Sextant, as the fifth of his 10 newly created constellations in Chapter VIII, De Numero Aſteriſmorum & Stellarum, tum nonnullis Rebus animadverſione dignis, of section Tabulae Solares Novae ("New Solar Tables") in the Prodromus. He formed the astronomical and navigational instrument from 12 faint stars in the space between Leo the Lion constellation and Hydra the Water Snake constellation. The sextant was constructed by Vulcan, ancient Roman mythology's god of fire and the forge, of blacksmithing and metalworking, noted Hevelius in his description of the celestial sextant. The instrument's fiery associations explain its placement between two "fiery" animals, the lion and the water snake.

Leo the Lion (center) with Uraniae Sextans (lower center) and Hydra the Water Snake (lower left); Hevelius's depiction from perspective of outsider looking into celestial globe reverses actual east-west appearance of sky for Earth-based observer as insider looking outward at celestial globe; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. FF: Public Domain, via ETH-Bibliothek e-rara

"Quintò; Uraniae Sextantem 12 planè novis Stellis exornatum, in perpetuum Rerum Coeleſtium memoriam, intra Aſtra referre placuit; quòd videlicet Vulcanus eundem Uraniae, in maximum commodum Aſtronomiae fabricaſſet, ac ingeniosè elaboraſſet; ut illius beneficio denuò Fixas obſervaret, corrigeret, plurimisq; novis hactenùs incognitis adaugeret; huncque etiam dictae Uraniae absq; remorâ, & omnni injectâ moleſtiâ ab Anno quinquageſimo octavo, menſe 27 Septembr. ad addnum 1679, 26. Sept. (donec obſervationes omnes, ad conſtruendum novum Fixarum Catalogum ſummè neceſſarias, aſſatim ex Coelo acquiſiviſſet) reliquerit; atque tum demum, ſed neſcio, quo malo & irato animo, per immane quoddam incendium, illum ſecum rursùs abſtulerit, ac magnâ vi Uraniae eripuerit. Quòd autem dictum Uraniae Sextantem inter Leonem Majorem, & Hydram referre voluerim, non ex eo accidit, quòd ſitus ſit convenientisſimus, novis Stellis reſertus; ſed eam ob cauſam, quòd Leo & Hydra animalia ſint ferè ignea, atque hic Sextans (ut cum Aſtrologis loquar) igneae omninò etiam videatur Conſtellationis. Nam profectò igneos cruciatus, à nefandis illis ignibus, cùm Vulcanus eum ſecum abduxerit, ſine dubio paſſus eſt," Hevelius explained (page 115).

Hevelius depicted his Sextans Uraniae (Urania's sextant) in Figure VV in Firmamentum Sobiescianum, the third volume of Prodromus Astronomiae. Figures in Hevelius's depictions of constellations are reversed, posed "back to front," as if on a celestial globe, as noted by English constellation history biographer Ian Ridpath (born May 1, 1947) in his post on "Hevelius and Firmamentum Sobiescianum" on his Star Tales website. The reversal of east and west differentiates depictions based upon the perspective of an outsider gazing into a celestial globe from depictions portraying the actual appearance of the sky to an insider looking outward, from Earth, at a celestial globe.

Three constellations neighbor Hevelius's dim Sextans the Sextant constellation. To the north, the front paws and one back paw of Leo the Lion, called Leo Majorem (Greater Leo, Leo Major) by Hevelius, are poised above the northern frame of the instrument's sectored shape. To the south and west, the head and upper body of Hydra the Water Snake writhe beneath Sextans' southern frame and southern arc. To the east, Crater the Cup balances, with a northeasterly tilt, on the mid-section of Hydra's wriggling body. Crater's western handle nears Leo's easternmost back paw.

Sextans (upper left) below the paws of Leo the Lion (uppermost left) and above the head and back of Hydra the Water Snake (center); Hevelius's depiction from perspective of outsider looking into celestial globe reverses actual east-west appearance of sky for Earth-based observer as insider looking outward at celestial globe; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. TT: Public Domain, via ETH-Bibliothek e-rara

With an area of 313.5 square degrees, Sextans the Sextant constellation occupies 0.760 percent of the sky, according to English astronomy writer Ian Ridpath (born May 1, 1947) in his table of constellations on his eponymous website (ianridpath.com). Sextans the Sextant's area places it as the 47th largest of the 88 constellations recognized by the International Astronomical Union (IAU).

Right ascension (abbreviated RA; symbol α) coordinates for Sextans the Sextant extend from 03 hours (h) 23 minutes (m) 20.8039 seconds (s) to 06h 00m 54.9367s, according to the constellation boundary tables on the International Astronomical Union's website. In the equatorial coordinate system, right ascension compares with terrestrial longitude.

Declination (abbreviated dec; symbol δ) coordinates for Sextans stretch from minus 1.3029516 to plus 31.1003609. The equatorial coordinate system's declination equates to geographic latitude.

Full visibility of constellation Sextans is available to Earth-based observers located between latitudes 78 degrees north and 83 degrees south. Stargazers positioned between latitudes 90 degrees north and 78 degrees north in the northern hemisphere and between 83 degrees south and 90 degrees south in the southern hemisphere experience partial visibility of the faint, small constellation (Ridpath, Constellations -- 2).

Constellation Sextans avails its best viewing from January through May, according to James Miller in "Star Constellation Facts: Sextans," posted April 23, 2017, on his website, Astronomy Trek. Locating the faint constellation by way of Regulus (Alpha Leonis, α Leonis; abbreviated Alpha Leo, α Leo), Leo the Lion's brightest star, eases Sextans the Sextant's findability, according to science writer Kelly Kizer Whitt in "Meet Sextans, the constellation of the sextant," published April 10, 2022, on the EarthSky website. Regulus shines only six degrees above Sextans' northern border.

Regulus marks the bottom of the backward question mark-shaped asterism, the Sickle, that defines the leonine constellation's head and shoulders. Sextans the Sextant's brightest star, Alpha Sextantis (α Sextantis; abbreviated Alpha Sex, α Sex), which marks the constellation's index mirror, lies to the south of Regulus.

Cancer the Crab (center) with Sextans (lower left corner) above the head of Hydra the Water Snake (lower left) and below the front paws and limbs of Leo the Lion (center left); Hevelius's depiction from perspective of outsider looking into celestial globe reverses actual east-west appearance of sky for Earth-based observer as insider looking outward at celestial globe; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. EE: Public Domain, via ETH-Bibliothek e-rara

Acknowledgment

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

Image credits:

(center) Sextans the Sextant constellation nestles between constellations Leo the Lion and Hydra the Water Snake; 17th-century Polish astronomer Johannes Hevelius named his constellatory astronomical instrument Sextans Uraniae (Urania's Sextant) after ancient Greek goddess Urania (Ancient Greek: Οὐρανία, Ouranía), who, among Greek mythology's nine inspirational Muses (Ancient Greek: Μοῦσαι, Moûsai), was honored as the muse of astronomy; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. VV: Public Domain, via ETH-Bibliothek e-rara @ https://www.e-rara.ch/zut/content/zoom/133967

Leo the Lion (center) with Uraniae Sextans (lower center) and Hydra the Water Snake (lower left); Hevelius's depiction from perspective of outsider looking into celestial globe reverses actual east-west appearance of sky for Earth-based observer as insider looking outward at celestial globe; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. FF: Public Domain, via ETH-Bibliothek e-rara @ https://www.e-rara.ch/zut/content/zoom/133939

Sextans (upper left) below the paws of Leo the Lion (uppermost left) and above the head and back of Hydra the Water Snake (center); Hevelius's depiction from perspective of outsider looking into celestial globe reverses actual east-west appearance of sky for Earth-based observer as insider looking outward at celestial globe; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. TT: Public Domain, via ETH-Bibliothek e-rara @ https://www.e-rara.ch/zut/content/zoom/133965

Cancer the Crab (center) with Sextans (lower left corner) above the head of Hydra the Water Snake (lower left) and below the front paws and limbs of Leo the Lion (center left); Hevelius's depiction from perspective of outsider looking into celestial globe reverses actual east-west appearance of sky for Earth-based observer as insider looking outward at celestial globe; J. Hevelii, Firmamentum Sobiescianum (MDCXC [1690]), Fig. EE: Public Domain, via ETH-Bibliothek e-rara @ https://www.e-rara.ch/zut/content/zoom/133937

For further information:

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Battistini, Pierluigi; Laura Peperoni; and Marina Zuccoli. "Szerdahely, Georg Aloys . . . . In his Historia Uraniae Musae Georg Szerdahely tells the tale of the origin of the constellation of Sextans: it was a gift of Apollo to Urania, which remained concealed to the human race, until Hevelius described it, in 1670: Instrumento astronomico, partem sextam Circuli complectente, quod Sextantem dicunt astronomi, olim Apollo donavit Uraniam in Parnasso coelestia dimetientem. Hunc subinde Phoebus (Urano sic jubente) inter astra retulit, mortalibusque incognitus fuit usque ad tempora cel. Hevelii, astronomi Dantiscani, a quo circa Annum 1670, dum catalogum Fixarum conderet, primum inter Leonem & Hydram repertus & observatus, atque subinde Aeri inter ceteras constellationes incisus cum astronomis sub nomine Sextans Uraniae, communicatus est." Astrophysics and Space Science Observatory of Bologna > Biblioteca > Vultus Uraniae > Illustrations From the Library of the Department of Astronomy University of Bologna > Astronomical Treatises Named After Urania.
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