Hier ist wahrhaftig ein Loch im Himmel. (Here is truly a Hole in Heaven.)
–  Sir William Herschel (18th Century)

Named after its silhouetted seahorse shape, the enigmatic Horsehead Nebula has intrigued generations of astronomers. Sir Patrick Moore wrote about the Horsehead Nebula in his Observer's Book of Astronomy (1962). The nebula was popularised in the 1980s by the photography of David Malin, who created many of the iconic images. Well into the 21st Century it is one of the top ten downloads at HubbleSite, and more questions are asked about the Horsehead Nebula than any other deep space object, according to professional astronomers. To celebrate the 11th anniversary of the launch of the Hubble Space Telescope in 2001, an Internet poll was undertaken to allow the public to vote for their favourite celestial image, with the winner being targeted by the Hubble. The Horsehead Nebula won.

Barnard 33

Just like the formation of the dark nebula itself is a mystery, the discovery of it is shrouded in intrigue. The Horsehead Nebula bears the scientific name Barnard 33 because it was first catalogued by EE Barnard using a 40-inch (1.02 metre) telescope in 1913, and his data was confirmed by work at Lick Observatory in 1919.

Astronomy Picture of the Day

The Astronomy Picture of the Day website states: 'Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s'. The photographic plate showing the Horsehead Nebula was taken with the Bache telescope in Cambridge, Massachusetts, on 6 February, 1888.

Edward Pickering

The SEDS website¹ declares: 'E Pickering detected IC 434 photographically in 1889'. IC 434 is the striking red emission nebula in Orion, which surrounds the Horsehead Nebula. The Pickering in this case is Professor Edward Charles Pickering (1846 - 1919), the Director of Harvard College Observatory, Cambridge, Massachusetts.

Williamina Fleming

However, we know that it was Pickering's assistant Williamina Fleming who identified IC 434 and the Horsehead Nebula in 1888, describing it thus:

A large nebulosity [IC 434] extending nearly south from zeta Orionis for about 60 minutes. More intense and well marked on the following side, with a semi-circular indentation 5 minutes in diameter 30 minutes south of zeta. Good plates of this region show this object, and it has been used here as a test for some time.

Williamina Fleming listed it as number 21 in her own 'Fleming' table and the official entry in the Harvard College Observatory records, Volume 60, dated 1908, on page 149 entry 62 lists the dark nebula as 'discovered by WP Fleming'.

Isaac Roberts

In 1902 Isaac Roberts, working on William Herschel's '52 Nebulous Regions', was intrigued by the sentence: Hier ist wahrhaftig ein Loch im Himmel (Here is truly a Hole in Heaven), and took it upon himself to investigate. Following the co-ordinates provided, Roberts describes the dark shape thus: an embayment free from nebulosity dividing it (IC 434) in halves.

Fleming 21

The Horsehead Nebula may have been Herschel's 'Hole in Heaven' but Williamina Fleming was the first scientist to measure and describe it, and log it as Fleming 21. This one light year² wide dark nebula, 1,500 light years distant, has since fired the imaginations of countless skygazers, but it will not always be there to enthral earthly viewers. This artistic cosmic creation, worthy of Michelangelo himself, is being dispersed by the proximity of a newly-born star, so human eyes can only enjoy the visual feast while they can.