Nebulae · dark

The Horsehead Nebula: a cloud shaped like a horse

The Horsehead Nebula, a dark horse-head shape against a pink glow, drawn in Exo-View

The Horsehead Nebula is a cold, dark cloud of dust and gas in the constellation Orion, 1,375 light-years away, shaped like the head of a chess knight. It shows only because it lies in front of a bright glow of hydrogen behind it. Exo-View lets you fly to it and see the pink glow with the dark horse against it.

Fly to the Horsehead Nebula See the Orion Nebula

Distance: About 1,375 light-years
Size: About 3.5 light-years from the ears to the throat
Kind: Dark nebula, a cloud of dust that blocks light
Catalogue number: Barnard 33; the glow behind it is IC 434
Found: In 1888 by Williamina Fleming, on a photographic plate
Seen in: The constellation Orion, just below Alnitak, the star at one end of the Belt

A shadow in the shape of a horse

The Horsehead is a knot of cold gas and dust that sticks out from a larger cloud, and it is opaque: it blocks the light behind it. The pink glow it stands against is hydrogen lit by a hot star nearby, Sigma Orionis. Williamina Fleming spotted the shape in 1888 on a photographic plate at Harvard, and it has been one of the most photographed objects in the sky since.

Seeing it

It is very hard to see by eye. It needs a dark sky, a fairly large telescope and a filter that passes only the glow of hydrogen, and even then it is faint. Long photographs show it well. It is near Alnitak, the star at one end of Orion's Belt, next to the Flame Nebula, in the same great cloud as the Orion Nebula.

Not for ever

The horse is slowly being worn away by the radiation of nearby stars, and may last only a few million more years before it disperses. At the scale of the stars, that is a short life.

In Exo-View

The button below flies from the Sun to the Horsehead. Its shape is made from photographs, so it is an artist's impression, and the plate says so.