The Dark Horse

*The famed Pipe Nebula which forms the horse’s rump and back leg. Image credit Hubble/ESO*

28 Jun 2017

I’ve always loved observing dark nebulae; there is something very strange about seeing what isn’t there, until you discover how many variations of darkness the eye can discern and the shapes they reveal: wisps of gentle darkness, rivers of deep darkness, pools of rich darkness, creeping tentacles of utter darkness. It takes time but in the different grades of darkness, foggy smoky details appear here and there, hinting at some sort of structure in the dark chasms of gas and dust.

Dark nebulae require very dark and very transparent skies – and, in my case, E.E. Barnard’s A Photographic Atlas of Selected Regions of the Milky Way on my observing table. (Thank goodness there was a 2011 reprint of this magnificent atlas!)

In these tremendous dark and transparent skies the magnificent sprawl of dark nebulae in Ophiuchus known as the Dark Horse is overwhelmingly obvious to the naked eye, an inky shadow against the brilliantly glowing Milky Way.

*The Dark Horse prancing through the most glorious field of stars. Antares is on the right of the image. Image credit Hubble/ESO*

I used my 10×50 binoculars to explore this gorgeous dark horse, although it is so big that it needs to be examined piecemeal, but what you lose in equine shape, you more than make up for with the sight of the various dark nebulae of different sizes, shapes and darknesses silhouetted against the brilliant Milky Way background. It really is a stunning field to examine in binoculars.

The horse comprises a fascinating jigsaw of dark nebulae. I’ve looked at the Pipe and Snake Nebulae many times, and squizzed the Dark Horse in a casual sort of way, but never before had I tried to discern the different equine body parts of the great prancing horse. Some of them were pretty obvious, others a little more obscure.

The horse’s rump and hind leg

B78, B65, B66, B67, and B59 (the Pipe Nebula)

The bowl of the pipe (B78) form’s the rump, the pipe’s stem (B65, B66, B67) form its leg and B59 forms its hoof. (It is just about to step on a very pretty little globular cluster NGC 6293, and indeed the dark horse appears to be prancing in a field scattered with some really gorgeous globular clusters.)

With the naked eye, the horse’s hind leg looks like a nearly straight dark cloud. However, when viewed through my 10×50 binoculars, variations in darkness and subtle details came to light and I could distinguish each of the connected dark clouds that form its leg and its hoof. It really is a gorgeous collection of dark nebulae, especially the way, down the length of its lovely leg, the stars crowd in on the shores of the nebulae.

Its upper rump, the whole B78 region, is amazing in the binos; the variations here and there in its shadowy darkness that made the nebula look as if it had been slightly crumpled, as subtle and almost-not-there as a black cloth tossed carelessly onto a black cloth – and the whole thing lying on a pile of scattered diamond dust. It really is a stunning star-filled setting for dark nebulae! An attractive roughly 6 mag star lies superimposed on the nebula just south of its centre.

The horse’s body

B74, B77 and B72

B74 is a beautifully inky-looking patch with crisp edges and lovely, very slightly yellowy, mag 7 HD 157588 attached to its southern end. B77 is a lovely pool of darkness with what look like rivers of slightly brighter darkness running randomly through the nebula. B72 – the Snake Nebula is a small S-shaped nebula that twists downwards from the north-north-west edge of the horse’s rump, looking like a careless loose rein. (As an extra treat, the very dark spot to the SW of the nebula is the gorgeous Ink Spot, B68.)

The horse’s front legs

Front near prancing leg: B63

The other front leg:B253, B246 and B60.

The dark horse’s near front leg is another lovely dark nebula; its concave curve to the south giving the horse its prancing motion. The west end of the nebula was very distinct, almost abrupt, while the east end faded away gently into the starry field. Its far front leg is a hazy, smoky nebulous region, a gauzy darkness against the starry background field.

The horse’s head

B268, B270, B259, B64, and B266.

The horse’s head lost its equine look in the binos, but its collection of nebulae were just gorgeous; lovely foggy, smoky shapes in the billowing clouds of Milky Way stars.

Globular cluster M9 is on the edge of B64 (a breathtakingly beautiful pairing in a telescope) and B259 has the small globular NGC 6342 on its edge. The two globulars were a treat – M9 is a pretty tough binocular object; knowing where it was helped pick it up, a small, hazy, round glow of light. And NGC 6342, after a bit of a search, appeared as a faint, very small, round droplet of pale light.

What a gorgeous horse to see prancing across our winter skies.