Comet C/2013 A1 Siding Spring, NEOWISE images. Time-lapse sequence showing four exposures of the comet (red) as it moved past the background stars. This long-period comet was discovered on 3 January 2013 by Robert H. McNaught at Siding Spring Observatory. Comets are icy bodies from the outer solar system that boil and form a bright tail of gas and dust as they approach the Sun. This image was obtained in infrared by NASA's NEOWISE (Near-Earth Object Wide-field Survey Explorer) on 28 July 2014.