Cat’s Eyes Asterism in Scorpius Rises Above Horizon in Northern Summer

Summary: The glowing Cat’s Eyes asterism in Scorpius the Scorpion constellation rises above the horizon in northern summer at mid-northern latitudes.

Cat’s Eyes asterism (lower left) in Scorpius the Scorpion constellation in Alexander Jamieson’s A Celestial Atlas (1822), Plate XIX: Public Domain, via U.S. Naval Observatory Library

In the Northern Hemisphere, the glowing Cat’s Eyes asterism, comprising Lesath and Shaula, in Scorpius the Scorpion constellation rises above the horizon in northern summer at mid-northern latitudes.

Scorpius the Scorpion constellation dominates the Southern Hemisphere’s skies as the southernmost zodiacal constellation. Zodiacal constellations reside along the plane of the ecliptic, which, from Earth’s perspective, is the sun’s apparent path across the sky.

In northern summer, at mid-northern latitudes, Scorpius the Scorpion rises entirely above the southern horizon. The constellation honoring the predatory arachnid reaches its highest point in the Northern Hemisphere’s nighttime skies in June, July and August.

Lying in the stinger at the tip of Scorpius the Scorpion’s curved tail, the Cat’s Eyes asterism brightly shines against the backdrop of the arching, hazy stream of white light traced by the solar system’s Milky Way galaxy across Earth’s nighttime skies. Scorpius the Scorpion is largely centered near the center of the Milky Way galaxy.

The Cat’s Eyes asterism in Scorpius the Scorpion constellation comprises two stars, known traditionally as Lesath and Shaula. The duo’s nickname as Scorpius the Scorpion’s stinger stars acknowledges their placement in the constellatory scorpion’s stinger.

Upsilon Scorpii (υ Scorpii; Upsilon Sco; υ Sco) is the eighth brightest star in Scorpius the Scorpion constellation. Based upon the Hipparcos (High Precision Parallax Collecting Satellite) Catalogue of precise astrometric (Ancient Greek: ἄστρον, ástron, “celestial body” + μέτρον, métron, “measure”) measurements of 118,218 stars, published in June 1997 by the European Space Agency (ESA), British astrophysicist Richard Powell lists the blue subgiant as the 115th brightest star in the nighttime sky.

The third magnitude star’s traditional name is Lesath. James B. “Jim” Kaler, American astronomer and University of Illinois professor emeritus of astronomy, notes the traditional name as deriving from mistranslations from Greek, Arabic and Latin. Lesath’s original Greek meaning, “foggy,” likely referenced Lesath’s nearness to, and pointing toward, Messier 7 (M7), a fuzzy naked-eye cluster in the Milky Way. The Arabic word las’a (“bite of a venomous animal”) occurs as a miscorrection of alascha, a Latinization of the Arabic word al laţkha ("the foggy patch”), by French scholar and self-taught polyglot Joseph Justus Scaliger (Aug. 5, 1540-Jan. 21, 1609).

Lambda Scorpii (λ Scorpii; Lambda Sco; λ Sco) shines as the second brightest star in Scorpius the Scorpion constellation. The second magnitude star ranks as the 24th brightest star in British astrophysicist Richard Powell’s Hipparchos-based list of the 300 brightest stars in the nighttime sky.

Lambda Scorpii’s traditional name of Shaula derives from al-šawlā´, an Arabic word meaning “raised tail.” The scorpion’s tail, often held in a forward curve over the predatory arachnid’s back, terminates in a pair of venom glands and a venom-injecting barb. Because of Lesath’s mismatched transcriptions, the traditional names of both of the stars in Scorpius the Scorpion’s Cat’s Eyes asterism now denote their status as the constellation’s stinger stars.

Shaula is actually a triple star system. The system’s primary star, designated as Shaula A, is a blue-white subgiant that fluctuates in brightness. With pulsation-driven, rapid fluctuations in brightness, Shaula is classified as a Beta Cephei star, a type of variable typified by Beta Cephei (β Cephei; Beta Cep; β Cep), a third magnitude star in Cepheus the Seated Aethiopian King constellation.

Shaula A’s two companions have short-period orbits. American astronomer Jim Kaler notes Shaula B’s orbital period as 2.96 years and Shaula Ab’s as 5.9525 days.

The takeaway for the Cat’s Eyes asterism in Scorpius the Scorpion is that the entire constellation, including the two stinger stars tipping the tail, rises above the horizon in northern summer at mid-northern latitudes in the Northern Hemisphere.

Cat’s Eyes asterism of Lesath and Shaula and other stars in Scorpius the Scorpion constellation: International Astronomical Union and Sky & Telescope, CC BY 4.0 International, via International Astronomical Union (IAU)

Acknowledgment

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

Image credits:

Cat’s Eyes asterism (lower left) in Scorpius the Scorpion constellation in Alexander Jamieson’s A Celestial Atlas (1822), Plate XIX: Public Domain, via U.S. Naval Observatory Library @ http://aa.usno.navy.mil/library/

Cat’s Eyes asterism of Lesath and Shaula and other stars in Scorpius the Scorpion constellation: International Astronomical Union and Sky & Telescope, CC BY 4.0 International , via International Astronomical Union (IAU) @ https://www.iau.org/public/themes/constellations/; (image URL @ https://www.iau.org/public/images/detail/sco/

For further information:

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Available @ http://www.cosmos.esa.int/web/hipparcos

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Available via U.S. Naval Observatory Library @ http://aa.usno.navy.mil/library/

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Available @ http://stars.astro.illinois.edu/sow/lesath.html

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Available @ http://stars.astro.illinois.edu/sow/shaula.html

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Available @ http://earthsky.org/constellations/scorpius-heres-your-constellation

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Available @ http://earthsky.org/brightest-stars/scorpion-stinger-stars-also-called-cats-eyes

Powell, Richard. “The Brightest Stars.” An Atlas of the Universe > Stars.
Available @ http://www.atlasoftheuniverse.com/stars.html

Rao, Joe. “Weekend Stargazing: Celestial Scorpion Reigns in Night Sky.” Space.com > Skywatching. June 28, 2013.
Available @ http://www.space.com/21757-weekend-stargazing-scorpius-constellation.html

Ridpath, Ian. “Scorpius the Scorpion.” Ian Ridpath > Star Tales.
Available @ http://www.ianridpath.com/startales/scorpius.htm

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Available @ http://www.constellation-guide.com/constellation-list/scorpius-constellation/

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Available @ http://www.solarsystemquick.com/universe/scorpius-constellation.htm