Barnard’s S Nebula
Edward Emerson Barnard (1857-1923) was a prolific astronomer. Among his many achievements were the discovery of Amalthea, the fifth moon of Jupiter (and the last ever to be discovered by visual observation), and the star that bears his name. Barnard’s star, a red dwarf 6 light years away, is the closest to the Sun after the 3 stars of the Alpha Centauri system, and it is notable for its rapid motion across our line of sight, changing position by some 10.3 arcseconds per year. Thus it has moved some 17 arcminutes since its discovery in 1916, or about half the width of the full moon. Coincidentally that’s about the length of the ‘S’ in the above image.
Barnard spent many years as professor of astronomy at the University of Chicago, where he used the world’s largest refractor (the Yerkes 40-inch) in a photographic survey of the milky way. In the course of this work he discovered a large number of dark nebulæ and showed that they are clouds of gas and dust obscuring the more distant stars.
Entry no. 72 in Barnard’s catalogue is informally known as the Snake nebula or the S nebula because of its distinctive shape, silhouetted against the myriad stars of the milky way, fittingly in the constellation of Ophiuchus, the serpent-bearer.
Below is a monochrome version of the above image in which the luminosity and red filters are combined. I cannot decide which version I prefer!
Having completed processing this image I realized I had photographed the area as part of a panoramic shot of the milky way while I was in Chile in 2019 (see here). I became curious as to whether the ‘S’ would be visible in that image.
So above I have reproduced the panoramic image at a smaller scale. Near the top is the Dark Horse nebula in which the S is found.
In this view the horse is upside down near top centre.
Above left is the boxed area from the panoramic image. This shows the Dark Horse, its head pointing right and with brilliant Jupiter at its front feet. The S is still far too small to be seen.
The right-hand zoomed image expands the centre part of the horse. With some effort the S can just be made out in the centre, lying at a 45° angle.
Still can’t see it? Some people can, others cannot. So below I have reproduced the last image with a typed ‘S’ superimposed over the actual ‘S’:
By shifting back and forth between the two images the dark ‘S’ should become visible.
It must be pointed out that this is a tiny part of a large panoramic image spanning 68° of the sky, and the image scale is about 47 arc-seconds per pixel. Compare this with the scale of 0.97 arc-second per pixel in the first image above and it’s no surprise that the ‘S’ is difficult to see!
Technical details (main colour image): Planewave CDK 14″ reflector with FLI Proline P09000 CCD camera. Total imaging time: 12 hours through Astrodon LRGB filters.
The monochrome image comprises the luminosity and red channels combined. Total imaging time 6 hours.
Images processed in PixInsight and Photoshop.
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