|Witch head nebula|
|Designation|| NGC 1909|
|Right ascension||05h 02m 00s|
|Declination||-07° 54′ 00″|
|Type of object||Reflection nebula|
|Dimensions||3° x 1°|
|Magnitude|| Apparent Mag: +13|
Absolute Mag: +6
|Distance from Earth||1,000 ly|
The Witch Head nebula (NGC 1909, IC 2118) is a reflection nebula in the constellation of Eridanus. Named for its resemblance to the profile of a witch, it is unusual for a reflection nebula in that it reflects the light of a single star, the star Rigel (Beta Orionis) in Orion. The Witch Head nebula cannot be seen with the naked eye as it is too faint, but can be located with a telescope to be 2.6 degrees west of Rigel. In fact, it is so faint that it was discovered photographically in 1909 by Max Wolf. The nebula has also appeared in works of science fiction, notably the TV series Andromeda.
Properties and Structure
Sources suggest the nebula is situated 800-1,000 light years from Earth. This means its apparent dimensions of a couple of degrees mean is roughly 50-70 light years across. The nebula appears blue as it reflects the light of the blue supergiant Rigel. The dust contained within the nebula scatters blue light more efficiently than red, enhancing this. This scattering is similar in nature to why the sky appears blue here on Earth.
Radio observations of the nebula have shown that it contains carbon monoxide. Six stars have been observed in the nebula, mainly T-Tauri stars, through observations made in the infrared using NASA's Wide-Field Infrared Survey Explorer. These T-Tauri stars are a type of variable star, that have a mass less that twice that of the Sun but a greater radius resulting in them being significantly brighter. The appearance of the nebula is likely due to strong stellar winds produced by nearby luminous stars. One of the stars may possess an orbiting "ring of gas and dust" and planets.