LDN 1235

Visual Appearance & Pareidolia: The cloud of interstellar gas and dust appears silhouetted against a rich star field and resembles a shark swimming through the cosmos. The dark absorption nebula is composed of thick microscopic dust grains that block the visible light of the background stars. Spanning roughly 15 light-years from "head" to "tail", the dust effectively acts as a veil blocking light.

Reflection Nebulae (vdB 149 & vdB 150): The Shark Nebula also contains small reflection nebula components where dust is lit by nearby stars, giving parts of the “shark” a subtle blue-gray glow. If you look closely near the head of the shark, you can find two small reflection nebulae (van den Bergh (vdB) 149 and vdB 150). These are visible because they are illuminated by the bright B8IC spectral type stars close by.

Extended Red Emission (ERE): The Shark Nebula is believed to be an extended red emission nebula (ERE). The dust in the nebula emits a faint red photoluminescence as it gets energized by the intense ultraviolet light of the young stars in the nebula. This means that in deep photographs, one can detect a dim red emission from hydrogen in and around the Shark Nebula, on top of the dust's silhouette.

History of Discovery: The Shark Nebula is located in Cepheus, one of the northernmost constellations in the sky. American astronomer Beverly T. Lynds noticed this dark cloud on the Palomar Observatory Sky Survey plates and in 1962 included it in her Catalogue of Dark Nebulae as LDN 1235. On those images, the dark portion corresponding to the "shark's eye" region appeared as an opaque patch blocking the background starlight.

Astrophotography Guide: Dark nebulae like this one are often difficult to process because they are extremely faint, and are difficult to bring out from the background medium due to how dark they are. The field often looks completely dark in short exposures, leading many to not expect any large nebula hiding there. The Shark Nebula is surrounded by Integrated Flux Nebula (IFN) and is itself full of interstellar gas, meaning advanced masking and stretch techniques are heavily utilized to reveal the structure.