The Black Eye Galaxy was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier in 1780. The dark dust feature was discovered by William Herschel, who observed M 64 twice in 1785 and 1789.
M 64 is well known among amateur astronomers. It is visible even in small telescopes, and can be glimpsed with good binoculars. It is a magnitude 8.5 spiral galaxy with apparent dimensions of 9.3 by 5.4 arc minutes. Visually, it exhibits an irregular shape with very uneven brightness and texture, overall a bright oval oriented about ESE-WNW, with a bright large core. The large dark lane on the disk, which resembles a “black eye”, gives rise to its nickname.
M 64 lies at a distance of is approximately 17 million light years, and is approximately 48,000 light-years across. At first glance, M 64 seems to be a fairly normal spiral galaxy. However, recent studies have led to the remarkable discovery that the interstellar gas in the outer regions rotates in the opposite direction from the gas and stars in the inner regions.
The galaxy’s inner region has a radius of approximately 3,000 light-years, while the outer section extends another 40,000 light-years. Active formation of new stars is occurring in the shear region where the oppositely rotating gases collide, are compressed, and contract.
Astronomers believe that the oppositely rotating gas arose when M 64 absorbed a satellite galaxy that collided with it, perhaps more than a billion years ago. The small galaxy that impinged on its neighbour has now been almost completely destroyed. Its stars have either merged with the main galaxy or scattered into space, but signs of the collision persist in the backward motion of gas at the outer edge of M 64.
M 64 forms a small group with the small irregular galaxy UGC 8024 (also known as NGC 4789A). It was also identified as a radio source, PKS 1254+21.