Earth and Space News: Northern Hemisphere winter asterism

Showing posts with label Northern Hemisphere winter asterism. Show all posts

Wednesday, January 11, 2017

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; credit Akira Fujii: Public Domain, via Wikimedia Commons @ https://en.m.wikipedia.org/wiki/File:Hubble_heic0206j.jpg

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; credit Akira Fujii: Public Domain, via Wikimedia Commons @ https://en.m.wikipedia.org/wiki/File:Hubble_heic0206j.jpg; CC BY 4.0 International, via ESA/Hubble @ https://esahubble.org/images/heic0206j/

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:

Byrd, Deborah. “See the Unicorn on Dark January Nights.” EarthSky > Tonight. Jan. 19, 2017.
Available @ http://earthsky.org/tonight/find-monoceros-the-constellation-of-the-unicorn-within-winter-triangle

“Canis Major Constellation.” Constellation Guide > Constellation List.
Available @ http://www.constellation-guide.com/constellation-list/canis-major-constellation/

“Canis Minor Constellation.” Contellation Guide > Constellation List.
Available @ http://www.constellation-guide.com/constellation-list/canis-minor-constellation/

Constellation Guide Admin. “Winter Hexagon.” Constellation Guide. March 13, 2016.
Available @ http://www.constellation-guide.com/winter-hexagon/

Couper, Heather; Nigel Henbest. The Story of Astronomy: How the Universe Revealed its Secrets. London UK: Octopus Publishing Group, 2012.

Darling, David. “Winter Hexagon.” The Worlds of David Darling > Encyclopedia of Science.
Available @ http://www.daviddarling.info/encyclopedia/W/Winter_Hexagon.html

Fujii, Akira. “Ground-Based Image of Orion, Canis Minor and Canis Major (Ground-Based Image).” Hubble Space Telescope > Images. Image release date: Dec. 13, 2005.
Available @ http://www.spacetelescope.org/images/heic0516d/

Hufnagel, Beth; Bob Stein. “16 Brightest Stars (Visible in the Northern Hemisphere).” Michigan State University Department of Physics and Astronomy > Courses > 1997 Spring.
Available @ https://www.pa.msu.edu/courses/1997spring/ISP205/sec-3/brightstars.html

Kunitzsch, Paul. Arabische Sternnamen in Europa. Wiesbaden, Germany: O. Harrassowitz, 1959.

MacRobert, Alan. “This Week’s Sky at a Glance, January 16-24.” Sky and Telescope > Observing > Sky at a Glance. Jan. 16, 2015.
Available @ http://www.skyandtelescope.com/observing/sky-at-a-glance/weeks-sky-glance-january-16-24/

Malin, David. “Constellations of Monoceros and Canis Minor.” David Malin Images > Akira Fujii > Constellations Indus to Virgo.
Available @ http://www.davidmalin.com/fujii/source/Mon.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

“Orion Constellation.” Constellation Guide > Constellation List.
Available @ http://www.constellation-guide.com/constellation-list/orion-constellation/

Ridpath, Ian. “The 25 Brightest Stars as Seen From Earth.” Ian Ridpath.
Available @ http://www.ianridpath.com/brightest.htm

Ridpath, Ian. “Canis Minor The Lesser Dog.” Ian Ridpath > Star Tales.
Available @ http://www.ianridpath.com/startales/canisminor.htm

Ridpath, Ian. “Orion the Hunter.” Ian Ridpath > Star Tales.
Available @ http://www.ianridpath.com/startales/orion2.htm

Sessions, Larry. “Procyon the Little Dog Star.” EarthSky > Brightest Stars. Feb. 25, 2016.
Available @ http://earthsky.org/brightest-stars/procyon-harbringer-of-the-dog-star

Snyder, Dave. “Introduction to the Constellations.” University of Michigan > University Lowbrow Astronomers > Guide. December 2003.
Available @ http://www.umich.edu/~lowbrows/guide/constellations.html

Staal, Julius D.W. The New Patterns in the Sky: Myths and Legends of the Stars. Blacksburg VA: McDonald and Woodward Publishing Co., 1988.

Thompson, Gary D. “The Entry of Arabic Star Names Into Europe.” Ancient Zodiacs, Star Names, and Constellations: Essays and Critiques. Last updated Nov. 3, 2016.
Available @ http://members.westnet.com.au/gary-david-thompson/page9q.html

Wednesday, January 4, 2017

Winter Hexagon Asterism Gathers Six Stars From Six Constellations

Summary: The Winter Hexagon asterism gathers six stars from six constellations for its prominent sky appearances from December to February.

asterism within an asterism: Winter Hexagon with Winter Triangle: Jim Thomas (Jomegat), Public Domain, via Wikimedia Commons

Also known as the Winter Circle or Winter Oval, the Northern Hemisphere's Winter Hexagon asterism gathers six stars from six constellations and also features an asterism within an asterism, the smaller Winter Triangle asterism, for its prominent sky appearances from December to February.

The six borrowed stars form a stellar hexagon that links them, outside of their individual constellations, in a recognizable pattern of stars known as an asterism. The six vertices, or angled meeting points of the imaginary hexagon’s six sides, are held by Auriga the Charioteer’s Capella, Taurus the Bull’s Aldebaran, Orion the Huntsman’s Rigel, Canis Major’s Sirius, Canis Minor’s Procyon and Gemini the Twins' Pollux.

In northern latitudes, the Winter Hexagon rises in the south. In December, the hexagonal asterism is high in the sky after midnight. Early January welcomes the Winter Hexagon’s highest point at around 11 p.m. In mid-February, the hexagon reaches its highest point around 8 or 9 p.m.

The Winter Hexagon is known as the Summer Hexagon or the Summer Circle in the Southern Hemisphere. English astronomer David Darling suggests extending the asterism southward, in the northern tropics and in the Southern Hemisphere, to include Canopus, the second brightest star in the southern constellation of Carina the Ship’s Keel.

Including Canopus, the second brightest star, after Sirius, in Earth’s night skies, would transform the Summer Hexagon into the Summer Heptagon, a seven-sided asterism. Amateur astronomer and Sky & Telescope contributor Bob King suggests a variant Winter/Summer Heptagon by adding Gemini’s Castor to the Winter Hexagon’s traditional sextet.

The Winter Hexagon asterism claims further structural interest for fueling the imaginations of stargazers. The hexagonal asterism contains another asterism within its asterismal boundaries by way of the Winter Triangle asterism. The Winter Triangle is an equilateral triangle that shares two vertices, Procyon and Sirius, with the Winter Hexagon. Orion’s Betelgeuse, located off-center inside the Winter Hexagon, tops the Winter Triangle.

High ranking brightness of all six stars explains the dramatic visibility of the Winter Hexagon asterism. All six appear in the list of 17 brightest stars in Earth’s night skies. Of those six, four (Sirius, Capella, Rigel, Procyon) are in the top eight.

Within the Northern Hemisphere’s brightest night stars, all six appear in the top 12 list. All except Pollux are in the top nine. The quartet of Sirius, Capella, Rigel and Procyon number in the Northern Hemisphere’s top six brightest night stars.

The Winter Hexagon is easy to locate because of its association with Orion. The Winter Hexagon encloses Orion and claims the constellation’s second brightest star, Rigel, as a hexagonal vertex. Rigel marks the constellation’s southwestern corner and the hexagon’s southwestern point.

The constellation of Greek mythology’s giant hunter dominates the sky as one of the night’s most conspicuous and most easily recognizable constellations. Orion’s brightest star, red supergiant Betelgeuse, marks the hunter’s right shoulder in front-facing depictions and his left shoulder in back-view illustrations. Rigel represents Orion’s left foot in front views and right foot in back views.

The Winter Hexagon is a showy asterism that shines on its own merits but also increases viewer interest with the dream catching possibilities of celestial bodies framed within the hexagon’s borders. Through its reliance upon Rigel, the Winter Hexagon always frames the recognizable magnificence of Orion the Hunter.

Apart from Orion’s constancy, other bright visitors also find themselves inside the Winter Hexagon. Amateur astronomer Bob King, known popularly as Astro Bob, noted the Winter Hexagon’s trapping of the waxing gibbous moon Saturday, Jan. 7, 2012, and Wednesday evening, Jan. 20, 2016. On Thursday, Jan. 9, 2014, Astro Bob shared Jupiter’s confinement within the Winter Hexagon.

The takeaway for the Winter Hexagon asterism is its wintry brightness as it brings together six bright stars from six familiar constellations for easy visibility from December to February.

Southern Hemisphere’s Summer Hexagon, visited by Jupiter; Winter Hexagon over Gensan, southern Philippines, Monday, Dec. 2, 2013, 22:27:28: peter jones (peterjonesdelacruz27), CC BY ND 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:

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

Astro Bob (Bob King). “Looking for Aurora Tonight? Check Out the Winter Hexagon + 2.” AreaVoices > Archives > January 2014. Jan. 9, 2014.
Available @ http://astrobob.areavoices.com/2014/01/09/looking-for-aurora-tonight-check-out-the-winter-hexagon-2/

Astro Bob (Bob King). “Moon and Winter Hexagon Bright on Bright Tonight.” AreaVoices > Archives > Jan. 7, 2012.
Available @ http://astrobob.areavoices.com/2012/01/07/moon-and-winter-hexagon-bright-on-bright-tonight/

Astro Bob (Bob King). “What Would It Look Like if Mars, Saturn or Neptune Replaced the Moon?” AreaVoices > Archives > February 2015.
Available @ http://astrobob.areavoices.com/2015/02/01/what-would-it-look-like-if-mars-saturn-or-neptune-replaced-the-moon/

Astro Bob (Bob King). “Wolf Moon Trapped by the Winter Hexagon.” AreaVoices > Archives > January 2016.
Available @ http://astrobob.areavoices.com/2016/01/19/wolf-moon-trapped-by-the-winter-hexagon/

Astro Bob (Bob King). “You Absolutely Must See the Winter Hexagon Tonight.” AreaVoices > Archives > January 2013.
Available @ http://astrobob.areavoices.com/2013/01/17/you-must-absolutely-see-the-winter-hexagon-tonight/

Constellation Guide Admin. “Winter Hexagon.” Constellation Guide. March 13, 2016.
Available @ http://www.constellation-guide.com/winter-hexagon/

Darling, David. “Winter Hexagon.” The Worlds of David Darling > Encyclopedia of Science.

Available @ http://www.daviddarling.info/encyclopedia/W/Winter_Hexagon.html

McClure, Bruce. “Winter Circle: Brightest Winter Stars.” EarthSky> Favorite Star Patterns > Science Wire. Jan. 10, 2016.
Available @ http://earthsky.org/favorite-star-patterns/winter-circle-highlights-brightest-winter-stars

Millás, Isolina V. “The Brightest Stars of the Southern Hemisphere.” Popular Astronomy, vol. 26 (June-July 1918): 387-391.
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://articles.adsabs.harvard.edu//full/1918PA.....26..387M/0000387.000.html

Ridpath, Ian. “The 25 Brightest Stars as Seen From Earth.” Ian Ridpath.
Available @ http://www.ianridpath.com/brightest.htm

Staal, Julius D.W. The New Patterns in the Sky: Myths and Legends of the Stars. Blacksburg VA: McDonald and Woodward Publishing Co., 1988.

“Winter Hexagon Over Stagecoach Colorado.” NASA’s Astronomy Picture of the Day (APOD).
Available @ http://apod.nasa.gov/apod/ap110103.html