During Northern Hemisphere summer nights, the galactic equator passes high overhead. This imaginary line traces the path taken across the sky of the Milky Way, the luminous band for which our galaxy is named. As we gaze along the plane of our disc-shaped home galaxy, we observe vast, glowing areas astronomers call H II regions--clouds of ionized hydrogen. This hydrogen is interspersed with tangled dark clouds of interstellar dust, the combination of the two providing the ingredients for the creation of countless stars.
Within the constellation of Cygnus, which straddles the galactic equator, gravity has arranged these glowing gas and dark dust clouds to resemble a major land form on our own planet. To its right is another area of red nebulosity that (somewhat) resembles a pelican. The North America Nebula and the Pelican Nebula are actually part of the same H II cloud. The shapes that Earth people find familiar are not two separate clouds of glowing hydrogen, but largely determined by the dust clouds in front of one larger hydrogen cloud.
The existence of these obscuring dust clouds is demonstrated by comparing many of the darker areas of the image with the reddish "North America" region. The darker regions show fewer stars, not because of an actual dearth of stars in that direction, but because of dust clouds that obscure the countless additional distant stars that exist in the more distant reaches of the galactic plane.
Two images, each made using a 400mm lens and a narrow-band light reduction filter, were joined together to record a wider section of the Milky Way. Each of the two images was a stack of multiple shorter exposures totaling 64 minutes.
Photo and notes Copyright, J. Hervat
NOTE: the Fine Art America watermark in the lower right does not appear on the print.
September 14th, 2020
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