Object Note
Nov 2, 2020    

IC 1831 is a streamer extending to the northeast from Sharpless 2-190, the Heart Nebula. The entire complex encompassing well over a degree in RA and two degrees in declination.

There are multiple associated catalog numbers encompassing this nebula complex as ever better observations and photography revealed fainter structure. NGC 896 being the bright knot in the northwest reach. IC 1805, the embedded star cluster at the center was first described by E. E. Barnard in the late 1890's. There is also IC 1795, a bright area of emission to the northwestern end of the complex also described by Barnard, and IC 1831, a faint streamer of emission to the northeast discovered by Max Wolfe in 1906.

Harold Corwin

IC 1831 may be a plume extending northeast from IC 1805. If so, its nominal declination, from a Heidelberg plate by Max Wolf, is at least one degree too far north. A one-degree field of the DSS2R plate, centered at 02 44.2, +62 09 shows a broad streak of nebulosity stretching southwest to northeast (note the different direction seen by Wolf, below). I think it is more likely that the object is a defect on the plate. This could, of course, be checked if the plate still exists. Here is Wolf's complete note from AN 4082, kindly translated by Wolfgang Steinicke:

A third [the first two are IC 2088 and IC 2177, both of which see] extended and pretty structured nebula was found at the border of Cassiopeia and Perseus. It measures many square degrees, too, irregularly covering a NW-SE oriented field, connecting some star groups while being crossed by many canals [dark streaks]. The center is approximately at RA = 2h 33m, Dec = +63d. This nebula is complicated, but unfortunately pretty faint, too. But I hope to reproduce a picture which was taken in December with the Bruce Telescope.

We should also search Wolf's papers from 1906 on to see if he actually did publish the photograph.

Another possibility is that the "nebula" is nothing more than the unresolved Milky Way, or even simple vignetting on Wolf's early plates.

― IC Notes by Harold Corwin

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