The Horsehead Nebula

The iconic Horsehead Nebula. Image credit Ken Crawford, Wikimedia Commons

1 Jan 2017

This was certainly a most fantastic way to start 2017! My first observation of the year was what has to be one of the most photographed but incredibly challenging blobs of darkness to observe visually – the Horsehead Nebula – which rises from a glowing sea of dust and gas like a giant seahorse in images.

I’ve observed it before but last night was one of those rare “best ever” observations that you’ll never forget.

While most agree that viewing this small dark patch superimposed over the faint streak of bright emission nebula IC 434 it isn’t an easy observation, a very dark and very transparent sky is what count. Light pollution renders the Horsehead Nebula invisible.

Williamina Fleming discovers the nebula

The Horsehead Nebula was discovered in 1888 by Williamina Fleming, a remarkable woman among that remarkable group of women known as the “Harvard Computers”. (The computers worked at the Harvard Observatory at the turn of the century; hired by the observatory’s director, Edward Charles Pickering, to catalogue and analyse thousands of photographic plates of stars – slices of the sky captured on glass; a repetitive and painstaking job.)

She discovered the Horsehead Nebula on HCO plate B2312. The photograph was taken on February 6, 1888 with the refracting 8-inch Bache Doublet telescope in Cambridge, MA. (This telescope would later be shipped off to Peru to take the first photometric data of southern stars.)

HCO plate B2312. Image credit Harvard College Observatory

This particular plate has a field of view of approximately 10º x 12.5º, and much of Orion is visible in the image. The women who examined these astronomical plates in detail used magnifying equipment, but it was their incredibly skilled eyes and unflagging concentration that really counted.

The image looks a little different than the modern full-colour high magnification images we’re used to when we think of the Horsehead Nebula!

Fleming described the bright nebula (now known as IC 434) that surrounds the Horsehead as having “a semicircular indentation 5 minutes in diameter 30 minutes south of Zeta Orionis.”

E.E. Barnard photographs the nebula

At Yerkes Observatory, on the night of July 27, 1913, astronomer E. E. Barnard turned the gaze of the world’s largest refracting telescope in the direction of Orion, targeting a mysterious object he’d tried to glimpse many times since his comet-hunting days decades earlier. Other astronomers had previously photographed the area, but the nature (and indeed, the very existence) of one fuzzy spot remained controversial.

*E.E. Barnard’s fabulous photograph of B33*

This night, however, there was no mistaking it: A crisp, black silhouette stood out against a bright background sky. Barnard wrote, “From the view, one would not question for a moment that a real object — dusty looking, but very feebly brighter than the night sky — occupies the place.” He also added, “This object has not received the attention it deserves.” He named it Barnard 33.

He also managed to capture a picture of the object, and to my eye it is the best photograph ever taken of the famed object, Hubble’s astonishingly beautiful and detailed images notwithstanding.

Observing the Horsehead Nebula

Last night, conditions were optimum. Superb dark sky. Stunning transparency. Fully dark adapted eyes. My 16″ f4.5 Dobs collimated to the back teeth. The H-Beta nebula filter at hand. Low magnification eyepieces at the ready.

And there it was.

We are used to seeing it as the small, distinctive shape on the the wide-angle images. In the eyepiece it is surprisingly large! There is no sign of its distinctive shape; it appears as a dark bay of darkness; IC 434’s ghostly ribbon looking like the faintest sliver of sheen when satin catches a faint light.

It was a wonderful sight.