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At approximately 430 light years from Earth, in the constellation of Ophiuchus, lies one of the nearest regions of star formation. The nebular complex normally referred to as Rho Ophiuchi (because the star Rho Ophiuchi lies about a degree to the north), is a mixture of dark nebulae and diffuse emission, with a mass 3000 times that of the Sun and covering a 4.5x6.5 degree area of sky. Within this nebula more than 400 infrared sources have been identified, mainly protostars and young stars no older than a million years.
The above image, recently released by NASA and obtained by the Wide-field Infrared Explorer (WISE), shows a variety of colours, and therefore wavelengths, which trace the various components of the complex. The bright region near the centre is an emission nebula excited by the light from the nearby star cluster, while the reddish region to the lower right is reflecting light from the star Sigma Scorpii. The area is nonetheless dominated by dark nebulae of dusty gas at temperatures of only 13-22 K, that are very opaque and impenetrable even for the infrared sensors of WISE.
As is clear from the image, the Rho Ophiuchi complex also contains a weave of filaments that slowly change their shape under the influence of stellar radiation pressure. The longest filaments are more than 50 light years long, but their width typically does not exceed 1 light year.
The colours in the image are false, but are coded to represent different infrared wavelengths so that the result resembles what we might see if our eyes were sensitive to infrared light.
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