Aquila Rift

Aquila Rift
Name	Aquila Rift
Type	Dark molecular cloud complex
Constellation	Aquila
Epoch	J2000
Distance	~200–3,000 pc
Major components	Serpens South, W40, M16 (neighboring), M17 (neighboring)
Notable objects	Serpens Main, W40, LDN 673, LDN 673

Aquila Rift

The Aquila Rift is a prominent dark molecular cloud complex in the northern sky that obscures background stars in the constellational region of Aquila (constellation), producing a broad rift visible along the Milky Way. It hosts extensive molecular gas, dust lanes, embedded young stellar objects, and active star-forming regions linked to larger complexes studied in surveys by observatories such as Spitzer Space Telescope, Herschel Space Observatory, Chandra X-ray Observatory, Very Large Array, and the Atacama Large Millimeter/submillimeter Array. Its structure and star formation activity connect to neighboring regions including the Serpens (constellation), Cygnus X (star-forming region), and complexes explored by projects like the Two Micron All Sky Survey and the Gaia mission.

Overview

The Rift is an extended concentration of dark nebulae and molecular clouds mapped in CO and extinction surveys by instruments such as the James Clerk Maxwell Telescope, FCRAO, IRAM, and the Green Bank Observatory. Historically charted on photographic atlases produced at the Palomar Observatory and incorporated into catalogues like the Barnard Catalogue and Lynds Dark Nebulae (LDN), it was later characterized in far-infrared by the Infrared Astronomical Satellite and mid-infrared by the Wide-field Infrared Survey Explorer. Studies by research groups at institutions including the Harvard–Smithsonian Center for Astrophysics, Max Planck Institute for Astronomy, and Caltech integrated multiwavelength data from the Sloan Digital Sky Survey and the WISE catalogues to refine its morphology.

Structure and Components

The Aquila Rift comprises a network of dark lanes and clumps catalogued as individual objects such as LDN 673, Serpens Main, Serpens South, W40 (H II region), and adjacent molecular clouds linked to the Pipe Nebula and Aquila Molecular Cloud Complex designations used in radio studies. Dense cores within the Rift are identified in submillimetre surveys by teams using the Submillimetre Common-User Bolometer Array and mapped in NH3 and N2H+ by groups at NRAO and MPIfR. Filamentary structures observed by the Herschel Gould Belt Survey resemble filaments seen in the Taurus Molecular Cloud and the Perseus Molecular Cloud, and contain prestellar cores comparable to those catalogued in the Orion Molecular Cloud Complex.

Distance, Size, and Mass

Distance estimates vary across subregions, with nearby components at ~200–300 parsecs on the near side and other clumps at ~1,000–3,000 parsecs as part of more distant spiral-arm complexes identified in CO surveys by the Dame et al. compilation and follow-up studies by teams at CfA and Max Planck Institute for Radio Astronomy. Angular extent on sky corresponds to tens of degrees and linear scales from several parsecs to hundreds of parsecs depending on adopted distances, analogous to spatial scales discussed for Perseus OB2 Association and the Scutum–Centaurus Arm. Mass estimates derived from CO, dust emission, and extinction mapping by authors affiliated with University of Arizona, University of Leeds, and JPL range from 10^3 to over 10^5 solar masses in aggregate, comparable to masses quoted for regions such as Aquila–Serpens complex and the Cepheus Flare in comparative studies.

Star Formation and Associated Objects

Active star formation in the Rift produces populations of protostars, Class I/II young stellar objects, and young clusters associated with regions like Serpens Main and Serpens South, identified in infrared and X-ray surveys by teams using Spitzer, Chandra, XMM-Newton, and ground-based near-IR facilities at Keck Observatory and Gemini Observatory. The W40 region hosts an H II region and OB-type candidates whose feedback shapes nearby filaments, drawing comparisons to feedback effects in NGC 2024 and RCW 38. Herbig–Haro objects, molecular outflows, and maser sources (e.g., methanol and water masers) within the Rift have been catalogued by groups from Jodrell Bank Observatory and the European Southern Observatory, analogous to outflows studied in HH 1/2 and VLA 1623. Embedded clusters have been cross-identified with catalogs maintained by the Two Micron All Sky Survey, UKIDSS, and the Vista Variables in the Via Lactea survey.

Observational History and Studies

The Rift’s dark lanes were noted on early star charts and in photographic atlases by observers at Harvard College Observatory and the Lick Observatory. Cataloguing efforts by Edward Emerson Barnard and Beatrice Tinsley-era observational programmes led to inclusion in the Barnard Catalogue and later extinction maps by Lynds and Dobashi. Radio CO mapping by teams at Bell Labs and Harvard–Smithsonian Center for Astrophysics refined kinematic structure; subsequent targeted studies were published by researchers affiliated with Princeton University, University of Vienna, Leiden Observatory, and the National Astronomical Observatory of Japan. Large surveys such as the Gould Belt Survey and the Galactic Plane Infrared Polarization Survey provided polarization and magnetic-field constraints complemented by theoretical modelling from groups at Caltech and MIT.

Visibility and Amateur Observation

From dark-sky sites the Rift’s obscuration is apparent along the Milky Way in late spring and summer in the Northern Hemisphere near constellations Aquila (constellation), Sagitta, Serpens (constellation), and Ophiuchus. Amateur astrophotographers and visual observers reference field guides from the Royal Astronomical Society and atlases produced at Palomar Observatory to locate features such as the dark lanes adjacent to bright stars like Altair and the star clouds near Gamma Aquilae. Imaging with small telescopes and DSLR cameras, and narrowband filters used by members of societies such as the Astronomical League and local American Association of Variable Star Observers chapters, reveal dust lanes and reflection nebulosity analogous to projects imaging the Dark Doodad Nebula and the Coal Sack Nebula.

Category:Dark nebulae Category:Molecular clouds Category:Star-forming regions