Optical image of the system M51 (the Whirlpool galaxy) which is formed by the spiral galaxy NGC 5194 (centre) and its companion, the irregular galaxy NGC 5195 (top). They are linked by a faint bridge of gas which is connected to one of the spiral arms of NGC 5194. This interacting couple lies some 13 million light years from the Earth in the constellation of Canes Venatici. The inner parts of NGC 5194 are populated by old yellow stars whereas much bluer and younger stars are present in the spiral arms. The central galaxy also shows several dark areas caused by clouds of dust which absorb the light here emitted.