Filamentary structures are apparent on large scales (as shown in the Planck image, right) and small scales (as seen in the Herschel image of a region in the Aquila constellation, left) in the Milky Way. The Planck image, covering a portion of the sky about 55°, was obtained by the High Frequency Instrument at a frequency of 857 GHz (corresponding to a wavelength of 350 micrometres). The dark horizontal band is the plane of our Galaxy, seen in cross-section from our vantage point. The colours represent the intensity of heat radiation by dust. The Planck image was obtained during the First Planck All-Sky Survey, which began in mid-August 2009 and is being completed now. By mid-March 2010, 98% of the sky had been observed by Planck, and 100% sky coverage is expected by late May 2010.