Winter Triangle Is Asterism Within Winter Hexagon Asterism

Summary: The Winter Triangle, which gathers three stars from three constellations, is an asterism within the Winter Hexagon asterism.

Winter Triangle of white Sirius (center foreground), white Procyon (upper left) and orange-red Betelgeuse (upper right); three stars of Orion’s belt below Betelgeuse; Rigel (right foreground), below Orion’s belt; ground-based image by Japanese amateur astronomer Akira Fujii shows constellations of Canis Major, Canis Minor and Orion: European Southern Observatory (ESO)/Akira Fujii, CC BY 4.0, via ESO @ http://www.spacetelescope.org/images/heic0516d/

The Winter Triangle, which gathers three major stars from three constellations, is an asterism within the Winter Hexagon asterism that rises high in Northern Hemisphere skies from December to February.

A recognizable pattern of stars, known as an asterism, may participate in an official constellation or may cull stars from more than one constellation. The Winter Hexagon gathers six stars from six constellations. The hexagonal asterism’s six sides are defined by Auriga the Charioteer’s Capella, Taurus the Bull’s Aldebaran, Orion the Hunter’s Rigel, Canis Major’s Sirius, Canis Minor’s Procyon and Gemini the Twins’ Pollux.

The Winter Triangle borrows two stars, Canis Major’s Sirius and Canis Minor’s Procyon, from the Winter Hexagon. Located within the space delimited by the Winter Hexagon, Orion’s Betelgeuse completes the triangular asterism.

The Winter Triangle’s stellar trio claim elite membership among the top nine brightest stars in Earth’s skies. Sirius, which is actually a binary star system, ranks as the brightest star in Earth’s night skies. Procyon and Betelgeuse hold eighth and ninth place, respectively. Procyon and Betelgeuse move up to the sixth and seventh spots in a ranking of brightest stars only primarily visible in the Northern Hemisphere.

Sirius marks the Winter Triangle’s southern apex. In Canis Major (“Greater Dog”), the night’s brightest star represents the constellatory dog’s nose.

Sirius's Bayer designation, devised by German celestial cartographer and stellar designator Johann Bayer (1572-March 7, 1625), is Alpha Canis Majoris (α Canis Majoris; Alpha CMi; α CMa). Its astronomical designation references Sirius’s status as the constellation’s brightest star. Its popular name derives from Ancient Greek (Σείριος, Seirios, "scorching").

Sirius’s binary star system comprises Sirius A, a white main sequence star, and its companion, Sirius B, a massive white dwarf. Near the horizon, Sirius appears as blue, red and white flashes to the naked eye. Sirius B is not visible to the naked eye.

Procyon marks the Winter Triangle’s northeastern apex. In Canis Minor (“Lesser Dog”), Procyon marks the constellatory dog’s side.

As with Sirius, Procyon is also a binary star system. Sirius A, a yellow-white main sequence star, is companioned by Procyon B, a white dwarf. The naked eye does not perceive Procyon B.

Procyon's Bayer designation is Alpha Canis Minoris (α Canis Minoris; Alpha CMi; α CMi). Its astronomical designation references Procyon’s rank as the brightest star in the Lesser Dog constellation. The bright star’s popular name derives from Ancient Greek (Προκύων, Prokyon, "before the dog"), reflecting Procyon’s appearance above the horizon before Sirius, known as “Dog Star,” in mid-northern latitudes.

Red supergiant Betelgeuse marks the Winter Triangle’s northwestern Apex. In Orion, Betelgeuse represents the ancient hunter’s shoulder. Face-front depictions find Betelgeuse in the mythical Greek huntsman’s right shoulder. Back-view depictions show Betelgeuse as Orion’s left shoulder.

Betelgeuse’s Bayer designation is Alpha Orionis (α Orionis; Alpha Ori; α Ori). Betelgeuse generally is the second brightest star in Orion. As a semi-regular variable star, though, Betelgeuse occasionally shines brighter than the constellation’s brightest star, multiple-star system Rigel.

Arabic philology expert Paul Kunitzsch (born July 14, 1930) traces the red supergiant’s popular name to a corruption of an Arabic descriptive phrase (يدالجوزاء, Yad al-Jauzā, “hand of al-Jauza”). Arab astronomy views Orion, with stars from northeastern constellatory neighbor Gemini the Twins, as a female figure known as al-Jauza (“the Central One”).

The three star’s triangular asterism encloses much of the constellation of Monoceros the Unicorn. The faint constellation hosts nebulae, such as the diffuse Rosette Nebula, and star clusters, such as open clusters Messier 50 (M 50; NGC 2323) and the Christmas Tree Cluster (NGC 2264). The Milky Way winds through Monoceros and the Winter Triangle and continues through the Winter Hexagon and beyond.

The takeaway for the Winter Triangle as an asterism within the Winter Hexagon asterism is the two-for-one enjoyment of stellar geometry, especially in the Northern Hemisphere’s wintry skies from December to February.

Winter Triangle asterism within Winter Hexagon asterism: Jim Thomas (Jomegat), Public Domain, 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:

Winter Triangle of white Sirius (center foreground), white Procyon (upper left) and orange-red Betelgeuse (upper right); three stars of Orion’s belt below Betelgeuse; Rigel (right foreground), below Orion’s belt: European Southern Observatory (ESO)/Akira Fujii, CC BY 4.0, via ESO @ http://www.spacetelescope.org/images/heic0516d/

Winter Triangle asterism within Winter Hexagon asterism: Jim Thomas (Jomegat), Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Wintersky.jpg

For further information:

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