Earth and Space News: Northern Hemisphere spring asterisms

Showing posts with label Northern Hemisphere spring asterisms. Show all posts

Wednesday, April 10, 2019

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:

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

Wednesday, April 3, 2019

Spring Triangle Asterism Is an Asterism Within Great Diamond Asterism

Summary: The Spring Triangle asterism is an asterism within the Great Diamond asterism, formed by triangulating three of the celestial gem’s four stars.

Spring Triangle of Arcturus, Denebola and Spica (red lines), an asterism within the Great Diamond asterism, 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 Spring Triangle asterism is an asterism within the Great Diamond asterism, formed by reimagining three of the celestial gem’s four stars into a triangular pattern.

In astronomy, the term asterism (Ancient Greek: ἀστερισμός, asterismós, “group of stars”) designates a recognizable pattern of stars. The pattern may occur within the borders of one constellation, as, for example, the Cat’s Eyes asterism in the stinger at the tip of Scorpius the Scorpion’s curved tail. An asterism may also be constructed of stars from two or more constellations. The Great Diamond asterism exemplifies an intra-constellatory asterism, uniting four stars from four constellations.

The Spring Triangle displays in Northern Hemisphere skies March to May as a distinctive asterism. Spring’s triangular asterism also participates in a larger asterism, the Great Diamond.

The Spring Triangle associates three of the Great Diamond’s stars and constellations. The triangular asterism concerns the neighboring constellations of Bootes the Herdsman and Virgo the Virgin and draws in Virgo’s western neighbor, Leo the Lion. Bootes contributes Arcturus while Denebola lies in Leo and Spica hails from Virgo.

Spica rates as the Spring Triangle’s only resident of the Southern Celestial Hemisphere, the southern half of astronomy’s imaginary celestial sphere. The northward and southward stretches of Spica’s parent constellation across the celestial equator qualify Virgo as an equatorial constellation. Bluish-white Spica lies 11 degrees south of the celestial equator.

Arcturus and Denebola are both located in the Northern Celestial Hemisphere. Arcturus’ parent constellation, Bootes, maintains borders exclusively in the Northern Celestial Hemisphere. Orange-reddish Arcturus perches 19 degrees north of the celestial equator. Bluish-white Denebola is sited in east central Leo, 15 degrees north of the celestial equator. Constellation Leo, however, briefly straddles the celestial equator in fulfillment of the Lion’s claim as Virgo’s western neighbor.

Spica also rates as the Spring Triangle’s only binary. Its primary and secondary members maintain a close orbital period of every four days.

Denebola and Spica serve as closest stars to radiants (apparent points of origin) of spring meteor showers. The annual activity dates for the showers appearing to radiate from Leo and from Virgo overlap with the Spring Triangle’s prominent display in Northern Hemisphere skies.

The radiant for the Beta Leonids meteor shower approaches Denebola. The Beta Leonid activity dates annually span Feb. 14 to April 25 and peak around March 20, according to American amateur astronomer and meteor expert Gary W. Kronk. The Alpha Virginids meteor shower occurs annually between March 10 and May 6, with maximum activity April 7-18.

The Spring Triangle’s parent asterism, the Great Diamond, gathers together the neighboring constellations of Virgo the Virgin and Bootes the Herdsman and their respective western neighbors, Leo the Lion and Canes Venatici the Hunting Dogs. Coma Berenices the Hair of Berenice constellation separates Bootes from Leo and also intervenes between Canes Venatici and Virgo.

Virgo’s Spica, Bootes’ Arcturus, Canes Venatici’s Cor Caroli and Leo’s Denebola depict the Great Diamond. Spica and Cor Caroli define the Great Diamond’s southern and northern vertices, respectively. Arcturus and Denebola demarcate the Great Diamond asterism’s eastern and western vertices, respectively.

The version of the Spring Triangle comprising Arcturus, Denebola and Spica excludes Cor Caroli from participation by reducing the diamond asterism to a triangular asterism. The Great Diamond’s Spring Triangle geometrically traces a nearly equilateral triangle, with all three sides of nearly equal length.

Joe Rao, Space.com’s Skywatching columnist, credits George Lovi (Aug. 14, 1939-Feb. 18, 1993), Sky & Telescope's Rambling Through the Skies columnist, with naming the Spring Triangle, possibly as an analogy with the Summer Triangle of Altair, Deneb and Vega. He notes that Henry M. Neely (1877-1963), lecturer at New York’s Hayden Planetarium, knew the asterism within the Great Diamond as the Virgo Triangle.

An alternative version of the Spring Triangle, however, shuns Denebola for Leo the Lion constellation’s brightest star Regulus. Poised 11 degrees north of the celestial equator, the bluish-white star system lies along the ecliptic, the sun's apparent path across Earth's skies. The alternative asterism presents an acute triangle.

The takeaways for the Spring Triangle asterism that is an asterism within the Great Diamond asterism are that the Alpha Virginids and Beta Leonids appear to radiate from two Spring Triangle stars, that the triangular asterism rejects Cor Caroli for Denebola and that an alternative Spring Triangle asterism retains Arcturus and Spica but replaces Denebola with Leo’s brightest star, Regulus.

Acknowledgment

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

Image credits:

Spring Triangle comprises an asterism within the Great Diamond asterism and forms from the Great Diamond's three southernmost stars: Kate (Friendlystar at English Wikipedia), Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Great_Diamond_map.gif

For further information:

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

Kronk, Gary W. "Alpha Virginids." Meteor Showers Online > Meteor Shower Calendar.
Available via Internet Archive Wayback Machine @ https://web.archive.org/web/20080516071922/http://meteorshowersonline.com/showers/alpha_virginids.html

Kronk, Gary W. "Beta Leonids." Meteor Showers Online > Meteor Shower Calendar.
Available via Internet Archive Wayback Machine @ https://web.archive.org/web/20080516071922/http://meteorshowersonline.com/showers/beta_leonids.html

Kronk, Gary W. Meteor Showers: An Annotated Catalog. Second Edition. The Patrick Moore Practical Astronomy Series. New York NY: Springer Science+Business Media, 2013.

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. "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. “Orion’s Belt Asterism Distinctively Dominates Winter Skies.” Earth and Space News. Wednesday, Jan. 18, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/01/orions-belt-asterism-distinctively.html

Marriner, Derdriu. “Summer Triangle of Altair With Deneb and Vega Dramatizes Summer Nights.” Earth and Space News. Wednesday, Aug. 10, 2016.
Available @ https://earth-and-space-news.blogspot.com/2016/08/summer-triangle-of-altair-with-deneb.html

Marriner, Derdriu. “Winter Hexagon Asterism Gathers Six Stars From Six Constellations.” Earth and Space News. Wednesday, Jan. 4, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/01/winter-hexagon-asterism-gathers-six.html

Marriner, Derdriu. “Winter Triangle Is Asterism Within Winter Hexagon Asterism.” Earth and Space News. Wednesday, Jan. 11, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/01/winter-triangle-is-asterism-within.html

Neely, Henry M. (Milton). A Primer for Star-Gazers. New York, NY; London, England: Harper & Brothers, 1946.

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

Whitworth, N. John. “Alpha Virginids Meteor Shower.” Universe Guide > Meteor Showers.
Available @ https://www.universeguide.com/meteorshower/alphavirginids

Whitworth, N. John. “Beta Leonids Meteor Shower.” Universe Guide > Meteor Showers.
Available @ https://www.universeguide.com/meteorshower/betaleonids