M63, also known as the Sunflower Galaxy, is a beautiful and spectacular spiral galaxy in the constellation of Canes Venatici. Along with M51, M94 and M106, it's one of four Messier galaxies located in the constellation. Of these, M51 or the Whirlpool Galaxy, is a much-studied interacting grand design spiral that claims the title of finest galaxy in Canes Venatici. However, M63 is only marginally fainter and not far behind its more illustrious neighbour. In addition, M63 and M51 are gravitationally bound and along with at least 6 other smaller galaxies they form the M51 Group of galaxies.
M63 is best seen from the Northern Hemisphere during the months of March, April or May.
This galaxy was the very first discovery made by Pierre Mechain, the great friend of Charles Messier, on June 14, 1779. On the same day, Messier included it in his catalogue. Although Canes Venatici is a faint constellation locating M63 is easy, since the famous Plough or Big Dipper asterism of Ursa Major can be used as a starting point. First locate Alkaid (η UMa - mag. +1.9) the eastern and end star of the Plough handle. Then imagine a line moving from Alkaid in a southwesterly direction for about 14 degrees. At the end of this line is the brightest star in Canes Venatici, Cor Caroli (α CVn - mag. +2.9). M63 is positioned about 2/3rds of the way along this line.
At magnitude +8.9, the Sunflower Galaxy is a challenging binocular object, appearing at best as an out of focus star. Through an 80mm (3.1 inch) refractor, it's recognisable as a galaxy but shows no detail. A 150 mm (6 inch) instrument at high powers reveals a bright core surrounded by a smooth shaped oval patch of nebulosity. Telescopes of 200mm (8-inch) aperture will start to show the spiral structure, including short arm segments. More subtle details, such as dust lanes, are visible in large amateur scopes.
M63 has an apparent size of 12.6 x 7.2 arc minutes and is located 37 million light-years away. It has an actual diameter of 135,000 light-years. In the early 1800's, Lord Rosse identified spiral structure within the galaxy, making this one of the first galaxies in which such structure was confirmed. It was listed as one of 14 "spiral nebulae" discovered to 1850.
In 1971, a magnitude +11.8 supernova appeared in one of the galaxy arms.
M63 Data Table
|13h 15m 49s
|+42d 01m 50s
|Apparent Size (arc mins)
|12.6 x 7.2
|Number of Stars
|Member of the M51 Group of galaxies