The Horsehead Nebula has changed over time, as seen in these images taken over the last ten thousand years
Location Orion Molecular Cloud complex Distance from Sol 1420 ly Length approx 81 ly
A dark nebula in front of the bright emission nebula IC 434, part of the massive Orion star formation complex. When first discovered in 81 BT by Williamina Fleming this dark cloud resembled a horse's head, hence the name. However since that time the cloud has changed considerably, affected by the pressure of starlight (mostly from Sigma Orionis, a nearby bright star) and by the strong, rapidly changing magnetic fields associated with several protostars buried deep within the dust.