A beautiful nebulous region located in the Perseus Arm of the Milky Way Galaxy, some 7500 light years from us within my personal favorite constellation of Cassiopeia. The object catalogued as Mel 15 is a young, 1.5 million year old open cluster containing several O and B stars around 50 M☉. The nebula around it, IC 1805 is an emission nebula with several dust lanes and darker cold molecular pillars

The grouping of stars located in the ridges on the right comprises the cluster. Most prominent are the giant stars mentioned above making up the overexposed regions, but the cluster also does contain some dimmer stars only a fraction of our Sun's mass. The giants may be bright and hot, but are short-lived with only 3-6 million year lifespans. The O and B stars produce intense stellar winds which have shaped the larger loops of the bubble of this region (only visible in wide-field images of the region, my catadioptric FOV is too narrow), as well as driving the formation of regions along the ridges where other stars form, cold molecular pillars analogous to the Pillars of Creation or the Double Helices of opaque nebulosity within the Rosette Nebula.

Cold molecular pillars, colloquially known as "elephant trunks," are a type of interstellar matter which can be found in molecular clouds. They form around bright, UV-emitting O and B class stars. The UV radiation does not ionize evenly throughout the nebula, and subsequently dense clumps of gas, known as evaporating gaseous globules or EGGs, are formed. These act as shields for gases behind them from stellar winds, and the columns of gas that get eroded away "downwind" of the EGGs, combined with the EGGs themselves, form the structures of the trunks. From what astronomers can tell from multi-wavelength EM studies, they consist of cold (20 K) cores surrounded by warm (60 K) gas with hot (250-320 K) outer shells. The most famous examples are the Pillars of Creation within M16 and the dark structures within the Rosette Nebula, though the presence of magnetic field interactions around C 50 cause the trunks to twist and wrap around one another, forming a double helix.

I enjoyed imaging this region very much. Gathering data at a northerly declination was easy, and color calibration in StarTools went well. The area of IC 1805 surrounding this region is relatively dark, as most of the gas is pushed toward the bubble's shock fronts. The entropy module in ST greatly allowed me to enhance the hydrogen around the cluster and near the dark nebula in the lower left.

Cheers and CS,

Lilith