Alternative Spring Triangle Asterism Replaces Denebola With Regulus

Summary: An alternative Spring Triangle asterism replaces Denebola with Regulus, Leo the Lion constellation’s brightest star.

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 Unported, via Wikimedia Commons

The Northern Hemisphere’s alternative Spring Triangle asterism replaces Denebola with Regulus to create an asterism comprised exclusively of first magnitude stars.

The alternative Spring Triangle asterism retains two stars, Arcturus and Spica, from the Spring Triangle asterism that participates in the Great Diamond asterism as an asterism within an asterism. The alternative Spring Triangle excludes Denebola in favor of Leo the Lion constellation’s brightest star, Regulus. The replacement of Denebola with Regulus disqualifies the alternative Spring Triangle from classification as an asterism within an asterism. Bypassing Denebola for Regulus places the alternative Spring Triangle’s western vertex outside of the boundaries of the Great Diamond asterism.

Astronomy defines a recognizable pattern of stars within one constellation or across constellations as an asterism (Ancient Greek: ἀστερισμός, asterismós, “group of stars”). The Goat Kids asterism occurs within Auriga the Charioteer constellation. Horse and Rider asterism appears as an asterism within the Big Dipper asterism in Ursa Major the Greater Bear constellation.

The Great Diamond exemplifies an asterism that crosses constellations. The Great Diamond culls four stars from four constellations. The prominent spring asterism comprises Arcturus in Bootes the Herdsman constellation, Cor Caroli in Canes Venatici the Hunting Dogs constellation, Denebola in Leo the Lion constellation and Spica in Virgo the Virgin constellation.

The alternative Spring Triangle asterism emerges from the association of three stars from three constellations. Bootes’ Arcturus represents the alternative Spring Triangle’s northern vertex. Virgo’s Spica marks the triangular asterism’s southern vertex. Leo’s Regulus anchors the alternative Spring Triangle’s western vertex.

The alternative Spring Triangle links stars of the same apparent visual magnitude, or scale of apparent brightness. Arcturus, Regulus and Spica all share first magnitude classifications. Retired NASA astrophysicist Fred Espenak identifies Arcturus’ apparent magnitude at minus 0.05. Retired University of Illinois astronomer James B. “Jim” Kaler details apparent magnitudes of 1.35 for Regulus and 1.04 for Spica.

Two different apparent magnitudes factor into the Spring Triangle asterism that is an asterism within the Great Diamond asterism. Denebola is a mid-second magnitude star. The bluish-white star’s apparent magnitude measures at 2.14. As first magnitude stars, orange-reddish Arcturus and bluish-white Spica shine brighter than Denebola.

The alternative Spring Triangle asterism honors the brightest stars in its three component constellations. Arcturus (Alpha Boötis, α Boötis; Alpha Boo, α Boo) rates as the brightest star in Bootes the Herdsman. Regulus (Alpha Leonis, α Leonis; Alpha Leo, α Leo) shines as the brightest star in Leo the Lion. Spica (Alpha Virginis, α Virginis; Alpha Vir, α Vir) claims maximum brightness in Virgo the Virgin.

Arcturus not only shines brightest in Bootes the Herdsman but also in the Northern Celestial Hemisphere, the northern half of astronomy’s imaginary celestial sphere. Arcturus’ brightness honors also include recognition as the fourth brightest star in the entire sky, encompassing both the Northern and the Southern Celestial Hemispheres. Sirius in Canis Major the Greater Dog, Canopus in Carina the Ship’s Keel and Rigil Kentaurus in Centaurus the Centaur reign, respectively, as the top three brightest stars in the entire sky.

Contrastingly, the Spring Triangle asterism within the Great Diamond asterism mixes stars of different brightness ranks within their home constellations. Denebola differs from Arcturus and Spica by not placing as its constellation’s brightest star. Denebola (Beta Leonis, β Leonis; Beta Leo, β Leo) occupies third place in Leo the Lion. Regulus and Algieba (Gamma Leonis, γ Leonis; Gamma Leo, γ Leo) rank as Leo’s first and second brightest stars, respectively.

The Great Diamond asterism’s Spring Triangle asterism and the alternative Spring Triangle asterism offer Earth-based observers the double optic of a triangular asterism within a triangular asterism. The two asterisms share the north-south side formed by Arcturus and Spica, respectively. The alternative asterism’s replacement of Denebola with Regulus does not erase the Great Diamond’s triangular asterism. Rather, extending to Regulus allows for two appearances by the Great Diamond’s Spring Triangle as an asterism within an asterism.

The takeaway for the alternative Spring Triangle asterism is that the replacement of Denebola with Regulus creates an asterism of same magnitude stars and allows for two occurrences by the version with Denebola as an asterism within an asterism.

The alternative Spring Triangle bypasses Leo’s Denebola for Leo’s Regulus; Regulus (mid-left) just above ISS (International Space Station) track, with Jupiter (center) to track’s right, Saturday, April 21, 2007: fdecomite, CC BY 2.0 Generic, via Flickr

Acknowledgment

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

Image credits:

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 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Spring_Triangle_(Stellarium).png

The alternative Spring Triangle bypasses Leo’s Denebola for Leo’s Regulus; Regulus (mid-left) just above ISS (International Space Station) track, with Jupiter (center) to track’s right, Saturday, April 21, 2007: fdecomite, CC BY 2.0 Generic, via Flickr @ https://www.flickr.com/photos/fdecomite/467456582/

For further information:

Espenak, Fred. “50 Brightest Stars.” AstroPixels > Stars > Bright Stars Photo Gallery.
Available @ http://astropixels.com/stars/brightstars.html

Espenak, Fred. “Arcturus.” AstroPixels > Stars.
Available @ http://astropixels.com/stars/Arcturus-01.html

Kaler, James B. (Jim). “Arcturus.” University of Illinois Astronomy Department > Star of the Week.
Available @ http://stars.astro.illinois.edu/sow/arcturus.html

Kaler, James B. (Jim). “Denebola (Beta Leonis).” University of Illinois Astronomy Department > Star of the Week.
Available @ http://stars.astro.illinois.edu/sow/denebola.html

Kaler, James B. (Jim). “Spica (Alpha Virginis).” University of Illinois Astronomy Department > Star of the Week.
Available @ http://stars.astro.illinois.edu/sow/spica.html

Lin, Ben; Jo Grant. “Arcturus.” SolStation > Stars.
Available @ http://www.solstation.com/stars2/arcturus.htm

Lin, Ben; Jo Grant. “Denebola.” SolStation > Stars.
Available @ http://www.solstation.com/stars2/denebola.htm

Marriner, Derdriu. “Discerning Alcor in Horse and Rider Asterism Tests 20/20 Vision.” Earth and Space News. Wednesday, May 31, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/05/discerning-alcor-in-horse-and-rider.html

Marriner, Derdriu. “Goat Kids Asterism Triangulates Near Golden Capella in Auriga.” Earth and Space News. Wednesday, Nov. 29, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/11/goat-kids-asterism-triangulates-near.html

Marriner, Derdriu. “Great Diamond Asterism Gathers Four Stars From Four Constellations.” Earth and Space News. Wednesday, March 27, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/03/great-diamond-asterism-gathers-four.html

Marriner, Derdriu. “Spring Triangle Asterism Is an Asterism Within Great Diamond Asterism.” Earth and Space News. Wednesday, April 3, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/04/spring-triangle-asterism-is-asterism.html

Rao, Joe. “The Spring Triangle.” Space.com > Skywatching. June 8, 2007.
Available @ https://www.space.com/2418-star-sight-celestial-diamond.html