Northern Cross Marks Autumn Nights From Nightfall to Midnight

Summary: The Northern Cross marks autumn nights from nightfall to midnight in the Northern Hemisphere as a prominent asterism in Cygnus the Swan constellation.

Northern Cross asterism in Cygnus the Swan constellation: Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons

As a seasonal indicator in the Northern Hemisphere, the Northern Cross marks autumn nights from nightfall to midnight via the asterism’s prominent perch within Cygnus the Swan constellation.

The Northern Cross emerges as an asterism, or recognizable pattern, of the five brightest stars in Cygnus the Swan. The distinctive asterism is visible year-round northward from mid-latitudes in the Northern Hemisphere.

After the splendor of nightlong prominence in summer, the Northern Cross announces autumn with visibility from nightfall to midnight. At nightfall, the asterism’s five stars appear high overhead. The Northern Cross reckons the closing of one day and the starting of another by setting in the northwest around midnight.

The Northern Cross configures the asterism’s length with three stars. Deneb marks the top while Albireo claims the base. As the asterism’s central star, Sadr pinpoints the intersection of the longer primary beam of the cross with the shorter crossbeam. Gienah and Delta Cygni are located at opposite ends of the crossbeam.

Deneb is the brightest star in both the Northern Cross asterism and its parent constellation. Deneb’s astronomical name is Alpha Cygni (α; Alpha Cyg; α Cyg). Its traditional name derives from dhaneb, an Arabic word for “tail.” The blue white supergiant’s distance from Earth is uncertain. Suggested distances range from 1,425 to 7,000 light years. Deneb lies in the swan’s tail.

Sadr is the asterism’s second brightest star. Its astronomical designation is Gamma Cygni (Γ Cygni; Gamma Cyg; Γ Cyg). Its traditional name derives from şadr, Arabic for “chest.” The bright yellow supergiant is distanced at 1,500 to 2,000 light years. Sadr’s central location in the constellation marks the swan’s breast.

Gienah is the third brightest star in the Northern Cross. Astronomically, Gienah is designated as Epsilon Cygni (ε Cyg; ε Cygni). Its traditional name derives from janah, Arabic for “wing.” Gienah lies at a distance of about 73 light years. The orange giant star marks the swan’s right wing.

Delta Cygni (δ Cygni; δ Cyg) is the asterism’s fourth brightest star. A traditional name, now obsolete, is Rukh, a Persian word for roc, a legendary bird of prey. Delta Cygni is actually a triple star comprising a blue white giant as the main star with a yellow white star as close companion and an orange star as a distant third companion. The triple star system is located about 170 light years away. Delta Cygni marks the swan’s left wing.

Albireo is the least bright star in the Northern Cross. Astronomically, it is designated as Beta Cygni (ß Cygni; Beta Cyg; ß Cyg). Its traditional name has a convoluted history of mistranslations of Arabic and Latin terms from its original name, ornis, the Greek name for Cygnus the Swan constellation. Albireo’s contrasting sapphire and gold colors are occasioned by its actual status as a double star. The larger star is an orange giant, with a blue star as the secondary component. Albireo lies about 430 lights years away. Albireo marks the swan’s beak.

The Northern Cross asterism not only participates in the swan constellation but also contributes its brightest star to another prominent Northern Hemisphere asterism, the Summer Triangle. Deneb forms the Summer Triangle with Altair, brightest star in Aquila the Eagle constellation, and Vega, the brightest star in Lyra the Lyre constellation. Deneb stands out as the brightest star in the Summer Triangle. Altair claims the honor of the asterism’s second brightest star.

At mid-northern latitudes in autumn, the Summer Triangle is visible from nightfall to early evening. Vega is positioned to the right, or west, of Deneb. Altair is sited below, or south, of Deneb.

The takeaway for Cygnus the Swan’s unmistakable asterism is that observers in the Northern Hemisphere know the Northern Cross as a seasonal marker. In autumn, the easily located asterism perches in night skies from nightfall to midnight.

Albireo, least bright star in Northern Cross, embellishes the asterism with contrasting amber and sapphire colors: Henryk Kowalewski, CC BY SA 2.5 Generic, 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:

Northern Cross asterism in Cygnus the Swan constellation: Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:CygnusCC.jpg

Albireo, least bright star in Northern Cross, embellishes the asterism with contrasting amber and sapphire colors: Henryk Kowalewski, CC BY SA 2.5 Generic, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Albireo_a.jpg

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