Whirlpool Galaxy. The Whirlpool Galaxy (M51, NGC 5194) is locked in a gravitational interaction with the smaller irregular galaxy NGC 5195 (orange, above M51). It is thought that NGC 5195 passed through the disc of M51 around 500 million years ago, then swung back through the disc to its present position behind M51 in the last 100 million years. M51 is around 50,000 light years in diameter, around half the size of our Milky Way. These two galaxies are around 37 million light years from Earth, in the constellation Canes Venatici. Captured from Cumeada Observatory, Reguengos de Monsaraz, Portugal.