10 hours of data collected in Narrowband -8.75 hours and 1.25 in RGB through RedCat51 with ASI2600mm on iOptron HEM27ec

Naming History and Classification

The Veil Nebula is a large, filamentary supernova remnant in the constellation Cygnus. The nebula is sometimes referred to as the Cirrus Nebula or Filamentary Nebula due to its delicate, thread-like structure. Portions of the nebula have various New General Catalogue (NGC) numbers, owing to its vast size and the visually distinct components observed by early astronomers. William Herschel cataloged several parts of the nebula as separate objects in the late 18th century, leading to NGC designations for its main arcs:

• NGC 6960: The Western Veil or “Witch’s Broom”
• NGC 6992 & NGC 6995: The Eastern Veil or “Network Nebula”
• NGC 6974 & NGC 6979: Luminous knots within the nebular complex
• IC 1340: The southern extension of the Eastern Veil
• Pickering’s Triangle: Also called Pickering’s Triangular Wisp or Fleming’s Triangle, situated between the Eastern and Western Veil

Description and Discovery

The Veil Nebula is visible in the sky as an intricate web of glowing gas, the aftermath of a star that exploded as a supernova. The original star is believed to have been about 20 times the mass of the Sun. The Veil Nebula is the visible part of the larger Cygnus Loop, a middle-aged supernova remnant.

Molecular Composition

TThe molecular composition of supernova remnants (SNRs) is complex and reflects both the material synthesized in the progenitor star and the interaction between the supernova ejecta and the interstellar medium.

Key molecules and ions observed in SNRs include:

• Carbon monoxide (CO): Both 12CO and 13CO isotopologues are common, tracing molecular gas in and around the remnant.
• Silicon monoxide (SiO): Including 28SiO and 29SiO, formed from silicon-rich ejecta zones.
• Formyl ion (HCO⁺) and sulfur monoxide (SO): Detected in young SNRs, indicating chemical mixing and molecular formation post-explosion.
• Hydroxyl (OH) masers: Especially at 1720 MHz, mark shock interactions between the SNR and adjacent dense molecular clouds.
• Other molecules: Including possible minor species and atomic ions (e.g., O, S, N, H) in various excitation states.

The distribution and abundance of these molecules depend on:

• The type and mass of the progenitor star.
• The dynamics of the explosion and subsequent mixing of ejected and ambient materials.
• The degree of interaction with dense interstellar or circumstellar molecular clouds, which influences the formation of new molecules and masers.

In remnants like SN 1987A, ALMA observations reveal distinct clumpy structures of CO and SiO, with variations in molecular abundance explained by mixing and radioactive heating during the first weeks after the explosion. The presence of HCO⁺ and SO in ejecta is a powerful indicator of post-supernova molecular formation, sometimes resulting from hydrogen mixing into carbon and oxygen zones.

For remnants interacting with molecular clouds, the shocked regions can compress pre-existing molecular gas, changing their density and chemistry. Such environments often show enhanced emission from CO, OH, and sometimes shock-tracing molecules like SiO and HCO⁺.

Overall, the typical molecular (and atomic/ionic) content found in SNRs includes:

• Major molecules: CO (carbon monoxide), SiO (silicon monoxide), HCO⁺ (formyl ion), SO (sulfur monoxide), OH (hydroxyl).
• Atoms and ions: O, S, N, H, and their ionized counterparts, often visible in optical and X-ray spectra.

Supernova remnants continue to enrich the interstellar medium by producing and dispersing these molecules and heavy elements into their surroundings.

Size, Expansion, and Age

• Distance from Earth: Estimated at 2,100 to 2,400 light-years
• Angular size: Spans about 3 degrees in the sky (roughly six times the diameter of the full Moon)
• Physical size: Approximately 110 to 130 light-years across
• Expansion Rate: The shock wave is moving outward at close to 1–1.5 million kilometers per hour (about 600,000 miles per hour)—nearly 1 million mph (450 km/s)
• Age: Estimates range from 5,000 to 20,000 years since the supernova explosion, with the most commonly cited figures between 8,000 and 10,000 years

Subcomponent NGC Objects (Summary Table)

Formation and Scientific Importance

The nebula is a powerful laboratory for studying shock physics and the enrichment of the galaxy with heavy elements. Before its detonation, the progenitor star expelled powerful stellar winds, carving out a cavity in the surrounding interstellar medium. The shock waves from the explosion now light up this cavity, producing the nebula’s distinctive filaments.

The Veil Nebula’s energetic shell interacts with the surrounding medium, forming a vast bubble of gas, dispersing heavy elements, and ultimately recycling stellar material that will go on to power future star and planet formation.

Visual Appearance

The Veil Nebula is renowned for its delicate, draped, and filamentary look—hence its poetic name—resembling a crumpled veil or net across the sky.

In summary: The Veil Nebula is an iconic, scientifically significant supernova remnant, noted for its spectacular structure, rich elemental content, and unique subcomponents, which have earned it multiple catalog designations and poetic names in the night sky