The 51st entry in Charles Messiers famous catalogue is perhaps the original spiral nebula--a large galaxy with a well defined spiral structure also catalogued as NGC 5194. Over 60,000 light-years across, M51s spiral arms and dust lanes clearly sweep in front of its companion galaxy, NGC 5195. The pair are about 31 million light-years distant. (NASA Media Archives). Buy this as a superb wall poster, a canvas print or a framed print.