Comet IRAS-Araki-Alcock

Comet Iras-Araki-Alcock was discovered by the Infrared Astronomical Satellite (IRAS) and made the closest known approach to earth of any comet within the last 200 years. This color image shows part of the 200,000 km long tail of warm dust stretching out behind the comet. In this image, made at a wavelength of 25 microns, the bright red area represents the unresolved nucleus of the comet, while the fainter emission from the tail of the comet is yellow and blue. Although the dust in the tail reflects most of the incident sunlight (making the tail visible optically), the dust also absorbs some of the sunlight which heats it, making the tail visible to IRAS.