Cygnus Molecular Nebula Complex

The Cygnus Molecular Nebular Complex (also known simply as the Swan Complex) is a giant molecular cloud located in the heart of the boreal Milky Way, in the direction of the constellation Cygnus. It is one of the most turbulent star-forming areas in the Milky Way Galaxy and its largest known molecular nebula complex. Within it are several H II regions, vast and brilliant stellar associations, open clusters, and a large number of some of the brightest stars in the galaxy.

The most notable structure in the complex is known by the catalog abbreviation Sh2-109; it is a vast ensemble, spanning hundreds of light-years, of H II regions, ionized by very bright stars, raddensated in the various OB Association found in this area of the sky. Sh2-109 is also the brightest and most prominent part of the huge molecular nebula complex known as Cygnus X; the total mass of gas and dust in this region is between 10,000 and 100,000 solar masses.

The region lies on the boundary between the Orion Arm, in which the Solar System is located, and the Perseus Arm, at a distance estimated at 5,000 light-years; the complex would still be in an early stage of its evolution, as would be evidenced by the presence of some extremely young and concentrated open clusters with bright and massive stellar components. In the furthest part of the region, connected to one of the OB associations in the area, is the well-known Cygnus X-1 object, an X-ray source thought by many to be a black hole sucking matter from its companion star, a blue supergiant.

The Cygnus complex is located in the direction of the stretch of sky between the bright star Deneb and Sadr, the heart of the Swan; however, neither with the naked eye nor with binoculars or a small telescope can detect it; what appears with a small instrument is a collection of aggregates of stars and small open clusters, which form a fairly obvious flare to the point that the stretch of the Milky Way of which they are a part is one of the brightest in the sky.

Being in the Northern Hemisphere at a declination of about +40°, the area of the nebula complex is perfectly observable from all the northern regions of the Earth, from which it appears visible for most of the year and, north of the 50th parallel north, even circumpolar; this branch of the Milky Way completely dominates the evening sky of the boreal summer and autumn, where it appears practically at the zenith at the northern mid-latitudes. From the Southern Hemisphere, on the other hand, this section of the sky is observable with great difficulty, especially from the mid-latitudes southward; in the southern tropical belt, however, it is fairly observable.

A powerful telescope is also needed to be able to notice the associated nebulosity, but the best method to be able to detect it is to take advantage of the potential of astrophotography; it should also be borne in mind that the part of the sky in which the cloud is condensed is largely obscured by a large complex of dark nebulae, known in the northern hemisphere as the Cygnus Fissure or "Boreal Coal Sack," which stands in the way of observer's line of sight.

Because of the phenomenon known as the precession of the equinoxes, the celestial coordinates of stars and constellations can vary significantly, depending on their distance from the north and south poles of the ecliptic.

Deneb, Sadr, and the Milky Way section of the Cygnus complex are at about 20h right ascension, not far from 18h, which is equivalent to the point at which, except the area around the north pole of the ecliptic, celestial objects reach their southernmost declination.