Whirlpool Galaxy

True to its name, two spiral arms sweep out from the center in a crisp swirl, as if the galaxy were water spinning down a drain — making it one of the most beautiful galaxies to photograph. The tip of one arm links like a bridge to a small yellowish companion galaxy (NGC 5195), creating the dramatic scene of a large galaxy seeming to draw in a smaller one.

The Whirlpool Galaxy (M51) is the archetypal "grand-design spiral," with arms that are sharply defined and symmetrically wound. It is a historic object: in 1845 the Earl of Rosse used his giant telescope to make the first drawing ever of a galaxy's spiral structure. Even now the small companion galaxy NGC 5195 is passing nearby and tugging at it with gravity — an interaction thought to compress the spiral arms even more sharply and trigger the birth of new stars in great numbers within them.