Seeing through the Dark
Astronomers have measured the distribution of mass inside a dark filament in a molecular cloud with an amazing level of detail and to great depth. The measurement is based on a new method that looks at the scattered near-infrared light or 'cloudshine' and was made with ESO's New Technology Telescope. Associated with the forthcoming VISTA telescope, this new technique will allow astronomers to better understand the cradles of newborn stars.
The vast expanses between stars are permeated with giant complexes of cold gas and dust opaque to visible light. Yet these are the future nurseries of stars to be.
Because the dust in these clouds blocks the visible light, the distribution of matter within interstellar clouds can be examined only indirectly. One method is based on measurements of the light from stars that are located behind the cloud.
Part of a filament in the Corona Australis molecular cloud. The image is a composite of J-, H-, and K-band near-infrared observations that were made with the SOFI instrument on ESO's NTT telescope in August 2006. The observations were made to test, how easily the scattered light can be observed and how good it is as a tracer of cloud structure. The J-, H-, and K-band intensities are coded with blue, green, and red colours. The gradual saturation of the near-infrared bands is visible as a change of colour. In diffuse regions the shorter wavelength J-band is strong and the colour is bluish. When the J-band saturates the colour changes first to green and finally, in the centre of the filament, the red colour corresponding to the K-band becomes the strongest. In the most saturated regions the surface brightness data can only be used to derive a lower limit for the total amount of dust on the line of sight.