The 8th-magnitude galaxy M51 in Canes Venatici, also known as NGC 5194. It is an Sc-type spiral seen nearly face-on, and was the first galaxy in which spiral structure was clearly seen, by Lord Rosse. It is interacting with a small irregular galaxy, NGC 5195, which appears to lie at the end of one of its spiral arms but is actually slightly behind it. The Whirlpool Galaxy lies about 25 million l.y. away.
Subjects: Astronomy and Astrophysics.