Van Den Bergh 149/50 and Lynds Dark Nebula 1235 by Tom Davis

Revealing The Undiscovered – Van Den Bergh 149/50 and Lynds Dark Nebula 1235 by Tom Davis

12 May , 2008 by

Over the past few weeks we’ve taken a look at some pretty incredible regions of space through astrophotography – Wolf Rayet stars, Thackeray’s Globules, tidal interactions and even giant dust clouds bursting with star birth. This time, let’s take a look at something so obscure that it might even be the first time that it’s been photographed…

What you’re looking at van den Bergh 149 (RA 22 09 08.5 Dec +72 53 05), van den Bergh 150 (RA 22 09 40.1 Dec +73 23 27) , and dark nebula LDN1235; Cepheus. According to image author, Tom Davis: “These two reflection nebulae are rarely imaged and this image may well be a premiere for amateur astroimaging. vdB 149 is the blue reflection nebula on the center left; vdB150 the center right. The darker nebula just “above” vdB150 is Lynds Dark Nebula 1235. It is likely an Extended Red Emission nebula (ERE). These ERE are galactic dark nebulae at high latitudes that become visible through illumination by the interstellar radiation field. ERE is a dust-luminescence process, which appears in a broad band extending in wavelength across the R-band (Schedler). This image is a composite-hybrid between two images taken with telescopes of different focal lengths. These nebulae have very low surface brightness and pose a significant challenge in imaging them. There are even fainter wisps of dust that make up the sky background. These small clouds are yet uncataloged as far as I can find through research. ”

In 1966, Sidney Van Den Bergh produced his own catalog of bright nebula with embedded stars. It contains information for “all BD and CD stars north of -33 deg which are surrounded by reflection nebulosity visible on both the blue and red prints of the Palomar Sky Survey. The nearer reflection nebulae lie predominantly along Gould’s Belt, whereas the more distant ones are concentrated to the galactic plane. The data outline 13 associations of reflection nebulae, some of which coincide with known OB or T associations. Attention is drawn to the fact that most reflection nebulae are illuminated by the integrated light of the Milky Way. The integrated radiation will be more intense above and below the galactic plane then in the galactic plane where the nuclear bulge of the Galaxy and most of the disk are obscured by interstellar absorption.”

Ninth magnitude vdB 149 first appeared in scientific literature around 1957 during a search for cepheids in galactic clusters done by Sidney Van Den Berg. Later, in 1960, it was also picked up by Halton Arp and more formally in 1966 when Van Den Berg did his “Study of Reflection Nebulae” utilizing the Palomar Sky Survey plates. It is also the 159th reflection nebula corresponding to HD 224403 (GLON=116.6, GLAT=-00.22) is introduced by R. Racine in his study of stars in Reflection Nebulae in 1968 where photometric and spectroscopic observations were done for fifteen distinct regions.

However, 8.4 magnitude vdB 150 holds a much more colorful history, having been noted in 1918 by Annie Jump Cannon and Edward Pickering. Annie picked it up again in 1925 during the extended Henry Draper Catalog Study and again in 1949 in a commemorative work done with Walton Mayall. From there, it laid dormant until 1991 and 1995 when revisited again by the Astrographic Catalogue for spectral type, proper motion and position. It holds its place in basic data as HD 210806 — Star in Nebula.

Like the Van Den Bergh catalogs of bright nebula where curtains of gas and dust conjoin with stars, the Lynds Dark Nebula catalog was developed in much the same way – compiled from studies of the red and blue prints from the Palomar Sky Survey. “The range in declination is from +90 to -33 degrees. A cloud had to be visible on both the red and the blue photographs in order to be recorded. It is therefore very probable that the more tenuous clouds which may be transparent in the red are not included herein. Lynds states that it was often difficult to detect a cloud that absorbed less than 0.75 magnitudes. Many of the small dark nebulae termed `Bok Globules‘ are not included in this catalog because they are apparent as dark objects projected against the bright background of an emission nebulosity: only objects which, on the basis of stellar density fluctuations, indicated the presence of absorption are contained here.”

Do these regions meet and produce new anomalies which need further study? I’d say that’s affirmative. It’s a well known fact LDN 1235 contains a variable star and that Lynd’s dark nebulae have differing turbulent velocities. There are areas where the opacity is weak and may very well have reached excitation temperatures – the density decreases and the temperature increases along the outward edges. Although it’s only conjecture on my part, I’d say that photographic studies like those done by Tom Davis are extremely important in the long term. They provide photographic record of changes not captured by professional observatories and will eventually become a source of future reference.

One that both amateur and professionals can study and enjoy…

This week’s awesome image is done by MRO member, Tom Davis. They were taken with an Astro Systeme Austria N12 f/3.5 Astrograph (LUM) and Takahashi FSQ-106 f/5 Astrograph (RGB) KAI-11000M – Total Exposure 10.6+ hours; LRGB 260:120:120:120 minutes, unbinned – April-May 2008; Inkom, ID, USA.

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