Sharpless 82 - wonderfuluniverse.de

Sharpless 82 – from remote

In 2025, I received a high-quality LRGB dataset of Sharpless-82 from Hellas Sky on the island of Crete. The data were made available to participants in the Hellas Sky Summer Contest, offering an excellent opportunity to process professional-grade astronomical data acquired under the exceptionally dark skies of southern Greece. The deep LRGB dataset reveals the nebula’s intricate emission structures while preserving the natural colors of the dense Milky Way star fields surrounding it.

Sh2-82 is a compact, mixed emission–reflection nebula in the constellation Sagitta, often nicknamed the Little Cocoon or Little Trifid Nebula because it resembles smaller versions of those famous objects.

Sh2-82 lies in the rich Milky Way star fields of Sagitta (the Arrow), in a heavily obscured region threaded with dark dust clouds. Its sky position is around right ascension 19h 29–30m and declination +18°, with an apparent size of only several arcminutes, making it much smaller than nebulae like the Trifid or the larger Cocoon. Distance estimates cluster around roughly 3,500–4,000 light‑years, placing it on the inner edge of the Orion (or Sagittarius) spiral arm of our Galaxy. The nebula is catalogued under several alternative designations, including LBN 29 and Bernes 17, and appears in lists of star‑forming regions as entry 843 in Avedisova’s catalogue.

Physically, Sh2-82 is an H II region embedded in a dark molecular cloud, wrapped in a reflection nebula; in other words, it is an active star‑forming pocket of gas and dust. The bright red emission core is produced by hydrogen gas ionized by the intense ultraviolet radiation of a hot, young, massive star at the center. That star is HD 231616, a blue main‑sequence or giant B0.5 star with a visual magnitude around 10, which provides most of the ionizing flux for the nebula.

Surrounding the emission region is a bluish reflection component, created when starlight is scattered by dust grains in the foreground dark cloud, notably the Lynds dark nebula LDN 727. This reflected light forms a cocoon‑like halo that bulges more strongly on one side, giving rise to the “Little Cocoon” nickname and to visual comparisons with IC 5146 (the Cocoon Nebula) and M20 (the Trifid Nebula).

Observations at infrared and radio wavelengths show that Sh2-82 hosts ongoing star formation. Several infrared sources have been detected within the cloud, including one object catalogued as IRAS 19282+1814 that coincides with methanol maser emission, a classic sign of a deeply embedded massive protostar. Compact radio sources of small angular diameter have also been identified, which further indicates that young stellar objects and dense ionized regions are developing inside the nebula. In broader Galactic context, Sh2-82 lies near the OB association Vulpecula OB4, a group of young, hot stars thought to have formed from the same large molecular complex.

Visually and in images, Sh2-82 shows a bright, roughly circular emission core about 5–9 arcminutes across, wrapped in a more diffuse, asymmetric reflection halo and crossed by nearby dark dust lanes. Deep photographs reveal a striking mix of red hydrogen emission, bluish reflection nebulosity, and silhouetted clouds, closely echoing the aesthetic of the larger Trifid Nebula but on a much smaller scale.

For observers, Sh2-82 is a relatively challenging target because it is small and lies in a cluttered, dusty Milky Way field, but it rewards long‑exposure imaging, especially with hydrogen‑alpha and O III filters that emphasize its ionized gas structures. From mid‑northern latitudes, Sagitta is well placed on late‑summer and autumn evenings, and with a moderately large telescope and suitable filters you can record both the emission core and the soft reflection halo that give this nebula its “little cocoon” character.

The data the calibration, registration, and final processing were performed in PixInsight. The result was as follows: