Messier 63 — Galaxy in Canes Venatici

M63 (NGC 5055), the Sunflower Galaxy, is a spiral galaxy in the constellation Canes Venatici, located approximately 29.3 million light-years from Earth. Classified as type SA(rs)bc, it is a flocculent spiral galaxy, meaning its spiral arms are patchy and discontinuous rather than the grand-design sweeping arms seen in galaxies like M51. At magnitude 8.6, it spans about 12.6 by 7.2 arcminutes, corresponding to a true diameter of roughly 98,000 light-years. The galaxy's disk is inclined about 55 degrees to our line of sight, presenting an elongated oval shape. M63 possesses a bright, compact nucleus surrounded by a complex inner structure with tightly wound spiral segments and prominent dust lanes. Deep imaging reveals an enormous stellar tidal stream looping around the galaxy, extending to over 160,000 light-years — a relic of a dwarf galaxy that was torn apart and absorbed. M63 is a member of the M51 Group, a small galaxy group that also includes the Whirlpool Galaxy. The galaxy hosts an active galactic nucleus classified as a Low Ionization Nuclear Emission-line Region (LINER).

Located in Canes Venatici, about 5 degrees northeast of the bright star Cor Caroli (Alpha CVn). In binoculars, M63 appears as a faint, elongated smudge. A 4-inch telescope at 80-100x reveals an oval glow with a noticeably brighter core. With an 8-inch telescope, the galaxy's disk becomes more extended, and hints of mottled texture from the patchy spiral arms may be glimpsed under excellent seeing. A 10-inch or larger telescope under dark skies can reveal some of the flocculent spiral structure as subtle brightness variations across the disk. Averted vision helps bring out the fainter outer regions. Best observed from March through July when Canes Venatici is high in the sky.

Discovered by Pierre Mechain on June 14, 1779. Charles Messier verified and cataloged it on the same day. Lord Rosse, using his 72-inch reflecting telescope at Birr Castle in the 1850s, was the first to observe and sketch the spiral structure of M63, making it one of the earliest galaxies recognized as having spiral arms. The galaxy played a role in the development of understanding galactic structure before the nature of galaxies as separate island universes was established.