NGC 4631 is an edge-on spiral galaxy in the constellation Canes Venatici. The galaxy appears slightly distorted due to gravitational interaction with its companion galaxy, NGC 4627. The slightly distorted wedge shape gives NGC 4631 the appearance of a herring or whale.
NGC 4631 was discovered by William Herschel in 1787. The name Herring Galaxy was first given in the Deep Sky magazine Interstellarum (No. 3, May-July 1995). The name "Whale Galaxy" first occurred in the Thompson and Bryan Supernova Search Chart series.
The Whale Galaxy is an enormous Sc type spiral galaxy seen edge-on. It has a visual magnitude of 9.8, and apparent dimensions of 17.0' x 3.5'.
NGC 4631 has a nearby companion dwarf elliptical galaxy, NGC 4627. The pair are included in the Arp Catalog of Peculiar galaxies as Arp 281. NGC 4631 and NGC 4627 are part of the NGC 4631 Group, a group of galaxies that also includes the interacting galaxies NGC 4656 and NGC 4657. This group of galaxies is between 25-30 million light years away.
The center of NGC 4631 contains a region of intense star formation. So many supernovae have exploded in the center of NGC 4631 that they are generating a "superwind" of ionized hydrogen gas blowing out of the plane of the galaxy. This superwind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.