On June 13, 2013 the Spitzer Space Telescope imaged comet ISON with its two available filters around 3.6 and 4.5 micrometers wavelength. The image on the left is the 3.6-micron image, dominated by dust reflecting sunlight, which is also drawn out as a little tail. On the right this dust component has been subtracted from the 4.5-micron image, leaving only a spherical shell of glowing gas.

NASA/JPL-Caltech/JHUAPL/UCF