Messier 63 or
M63, also known as
NGC 5055 or the seldom-used
Sunflower Galaxy, is a
spiral galaxy in the northern
constellation of
Canes Venatici with approximately 400 billion stars. M63 was first discovered by the French astronomer
Pierre Méchain, then later verified by his colleague
Charles Messier on June 14, 1779. The galaxy became listed as object 63 in the
Messier Catalogue. In the mid-19th century, Anglo-Irish astronomer
Lord Rosse identified spiral structures within the galaxy, making this one of the first galaxies in which such structure was identified.The shape or morphology of this galaxy has a
classification of SAbc, indicating a spiral form with no central
bar feature (SA) and moderate to loosely wound
arms (bc). There is a general lack of large-scale continuous spiral structure in visible light, so it is considered a
flocculent galaxy. However, when observed in the
near infrared, a symmetric, two-arm structure is seen. Each arm wraps 150° around the galaxy and extends out to 13,000
light-years (4,000
parsecs) from the nucleus.M63 is a weakly
active galaxy with a
LINER nucleus – short for 'low-ionization nuclear emission-line region'. This displays as an unresolved source at the galactic nucleus that is cloaked in a diffuse
emission. The latter is extended along a
position angle of 110° relative to the
north celestial pole, and both
soft X-rays and hydrogen (
H-alpha) emission can be observed coming from along nearly the same direction. The existence of a
supermassive black hole (SMBH) at the nucleus is uncertain; if it does exist, then the mass is estimated as (8.5±1.9)×108
M☉, or around 850 million times the mass of the Sun.
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