Friday, October 26, 2012

43rd Week - The cometary star forming region G110-13

The northern Milky Way in the area over cipher Cassiopeia to Peruses is rich in interstellar matter. There are not only bright H II regions, but also reflection nebula and a lot of dark dust and molecular clouds. The current Academy of Sciences demonstrates a very nice example of a combination of molecular cloud and reflection nebula, namely, a brownish, elongated cloud in the border area Andromeda and Cassiopeia. 

This cloud is called G110-13, reflecting the galactic coordinates. The elongated shape reminiscent of a comet. The lighter head (right) followed by a short neck, strangled three stars. It extends to the left tail-like appendage in the northeast. Points north of the brightest nebulae games from the upper left corner.
This unusual form was the reason why the cloud extensively investigated in the 1980's and 90's in all possible wavelengths, to understand their dynamics. The dimensions of the G110-13 amount to 1.4 ° in length and approximately 8 to 12 "in width. Apparently it has been in the interior of the densest places of star formation, because at least three stars of spectral type B8-B9 are clearly associated with the molecular cloud. At the northeastern tip G110-13 bends sharply to 90 ° from the northwest.

On the websites of various astrophotographers the molecular cloud G110-13 is referred to as vdB 158th This is incorrect because vdB 158 is only a tiny fraction of G110-13 in reality. We recognize vdB 158 as a small diffuse, blue reflection nebula in the "neck region". Sidney van den Bergh (vdB) had the photographic glass plates of the Palomar Observatory Sky Survey (POSS) searched for such reflection nebulae in the 1966 arranged in a catalog. In the first place we went to him like blue glowing mist, illuminated by young low-mass stars, the energy is not sufficient for the ionization of hydrogen and therefore the H-alpha emission from the surrounding nebula.

Enlightening star for vdB 158 is the main sequence star HD 222142 (BD +47 ° 4220) with the spectral B8V (read: "be eight five", because the attached "V" is a Roman "5" to identify the luminosity class of the star). Like the apparent magnitude of this star is 9.66 and 9.55 in the blue like in the visuals, so that a color index BV = 0.11 may result, which corresponds to a light blue. Adjacent are two more stars that form with HD 222142, the aforementioned small triangle on the neck of G110-13. First, the HD 222106 (= BD +47 ° 4216), a K0-star in the picture just above HD 222142nd It is like I do in the Blue 9.84 and 8.34 in the visible light, thus with BV = 1.50 clearly likes orange. These are some of them even joined the right HD 222086 (= BD +47 ° 4214) with the spectral type B9, a visual magnitude of 8.51 mag and the color index BV = 0.00 likes and that is bright blue.

Image author Slotosch Frank, a member of the VdS Section astrophotography. He took from the premises of the Vogelsberg this interesting field with a Takahashi FSQ-106 refractor on at 500 mm focal length. With a color camera FLI 4022c was exposed 28 x 10 min.

RA = 23 h 37 min 52 s, Dek = +48 ° 48 29 '''

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