Great Diamond Asterism Gathers Four Stars From Four Constellations

Summary: The Great Diamond asterism gathers four stars from four constellations for its prominent spring sky appearances in the Northern Hemisphere.

The Great Diamond asterism comprises Canes Venatici's Cor Caroli, Leo's Denebola, Virgo's Spica and Bootes' Arcturus, with the Spring Triangle, an asterism within an asterism, formed by Arcturus, Denebola and Spica: Kate (Friendlystar at English Wikipedia), Public Domain, via Wikimedia Commons

The Great Diamond asterism gathers four stars from four constellations, displays prominently in the Northern Hemisphere’s spring skies and contributes its three southernmost stars to an asterism, the Spring Triangle, within its asterism.

An asterism is a recognizable pattern of stars. Asterisms may be confined within the boundaries of one constellation, as, for, examples, Orion’s Belt asterism in Orion the Hunter constellation. Asterisms also may emerge by sharing stars from two or more constellations, as, for example, the Winter Hexagon asterism of six stars from six constellations.

The Great Diamond is an intra-constellatory asterism. The Great Diamond comprises Spica in Virgo the Virgin, Arcturus in Bootes the Herdsman, Cor Caroli in Canes Venatici and Denebola in Leo the Lion.

The Great Diamond forms from neighbors and neighbors of neighbors. Virgo lies south of Bootes and of Leo. Bootes resides north of Virgo and east of Canes Venatici.

The four constellations that unite in the Great Diamond asterism have borders in the Northern Celestial Hemisphere, the northern half of astronomy’s imaginary celestial sphere. Leo and Virgo are equatorial constellations that straddle the celestial equator. Bootes and Canes Venatici reside entirely within the Northern Celestial Hemisphere.

Spica marks the Great Diamond’s southern vertex. The bluish-white star system reigns as the brightest star in Virgo the Virgin constellation. The first magnitude star lies south of the celestial equator in Virgo’s Southern Celestial Hemisphere reach. Spica is the traditional name for Alpha Virginis (α Virginis; Alpha Vir, α Vir). The variable, spectroscopic binary’s traditional name derives from Latin (spīca) for the “ear of corn or grain” that Virgo holds in her left hand. As a spectroscopic binary, Spica’s primary and secondary members are detectable by a Doppler shift in their spectra’s absorption lines.

Arcturus represents the Great Diamond’s eastern vertex. Arcturus shines as the brightest star in Bootes the Herdsman constellation. The first magnitude star lies in southern Bootes, 19 degrees north of the celestial equator. Arcturus is the traditional name for Alpha Boötis (α Boötis; Alpha Boo, α Boo). The orange-reddish star’s traditional name derives from Ancient Greek (Ἀρκτοῦρος, Arktouros) for “guardian of the bear.” Ursa Major the Greater Bear constellation lies northwest of Arcturus.

Cor Caroli anchors the Great Diamond’s northern vertex. Cor Caroli is the brightest star in Canes Venatici the Hunting Dogs constellation. The binary star’s combined apparent magnitude of 2.81 qualifies third magnitude Cor Caroli for nearly second magnitude status. Cor Caroli lies in west central Canes Venatici, 38 degrees north of the celestial equator.

Cor Caroli is the common western name for Alpha Canum Venaticorum (α Canum Venaticorum; Alpha CVn, α CVn). The common name, which derives from Latin for “heart of Charles,” appeared in the 17th century. American naturalist and amateur astronomer Richard Hinckley Allen (Aug. 4, 1838-Jan. 14, 1908) considered the name as honoring King Charles II of England (May 29, 1630-Feb. 6, 1685). English science writer Ian Ridpath associates Cor Caroli with King Charles I of England (Nov. 19, 1600-Jan. 30, 1649).

Denebola perches at the Great Diamond’s western vertex. Professor Emeritus of the University of Illinois James B. “Jim” Kaler describes Denebola as “marginally third brightest after binary Algieba” in Leo the Lion constellation. The bluish-white star lies in east central Leo, 15 degrees north of the celestial equator. Denebola is the traditional name for Beta Leonis (β Leonis; Beta Leo, β Leo). The mid-second magnitude star’s traditional name derives from Arabic (ðanab al-asad) for “tail of the lion.”

Astronomy popularizer H.A. (Hans Augusto) Rey (Sept. 16, 1898-Aug. 26, 1977) renamed the Great Diamond as the Virgin’s Diamond. The German-born American author and illustrator redrew constellations to make them more intuitive than the traditional visualizations. Rey co-created the Curious George series of children’s picture books, between 1941 and 1966, with his wife, Margret (May 16, 1906-Dec. 21, 1996).

The Spring Triangle exists as an asterism within an asterism. The three stars south of the Great Diamond’s northern apex, Cor Caroli, reimagine their geometry to form the Spring Triangle. An alternative Spring Triangle bypasses Leo’s Denebola for Leo’s Regulus.

The takeaway for the Great Diamond asterism, which gathers four stars from four constellations, is that the prominent spring asterism formed by Virgo’s Spica, Bootes’ Arcturus, Canes Venatici’s Cor Caroli and Leo’s Denebola is that Arcturus, Denebola and Spica also form an asterism within the Great Diamond asterism as the smaller Spring Triangle asterism.

Spring Triangle of Arcturus, Denebola and Spica (red lines) and alternative Spring Triangle of Arcturus, Regulus and Spica (green lines): Elop using Stellarium, 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:

The Great Diamond asterism comprises Canes Venatici's Cor Caroli, Leo's Denebola, Virgo's Spica and Bootes' Arcturus, with the Spring Triangle, an asterism within an asterism, formed by Arcturus, Denebola and Spica: Kate (Friendlystar at English Wikipedia), Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Great_Diamond_map.gif

Spring Triangle of Arcturus, Denebola and Spica (red lines) and alternative Spring Triangle of Arcturus, Regulus and Spica (green lines): Elop using Stellarium, CC BY SA 3.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Spring_Triangle_(Stellarium).png

For further information:

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Available @ https://earth-and-space-news.blogspot.com/2016/08/summer-triangle-of-altair-with-deneb.html

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Available @ https://earth-and-space-news.blogspot.com/2017/01/winter-hexagon-asterism-gathers-six.html

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