User:SkyFlubbler/sandbox/Messier 63



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. A member of the nearby M51 galaxy group, it hosts approximately 400 billion stars. It is also an active galaxy possessing a LINER-type H II active galactic nucleus - one of the closest such galaxies to Earth. It was first described by the French astronomers Pierre Méchain and Charles Messier in 1779, which then included the galaxy in the now-famed Messier Catalogue.

Discovery and pre-20th century observations
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, initially being described as a faint, nebulous patch:

"63. 13h 04m 22s (196d 05' 30") +43d 12' 37" (June 14, 1779)

`Nebula discovered by M. Méchain in Canes Venatici. M. Messier searched for it; it is faint, it has nearly the same light as the nebula reported under no. 59 Messier 59 : it contains no star, & the slightest illumination of the micrometer wires makes it disappear: it is close to a star of 8th magnitude, which precedes the nebula on the hour wire. M. Messier has reported its position on the Chart of the path of the Comet of 1779 C/1779 A1 (Bode) .'"

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 4000 pc 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 $850,000,000 solar mass$, or around 850 million times the mass of the Sun.

Radio observations at the 21-cm hydrogen line show the gaseous disk of M63 extends outward to a radius of 40 kpc, well past the bright optical disk. This gas shows a symmetrical form that is warped in a pronounced manner, starting at a radius of 10 kpc. The form suggests a dark matter halo that is offset with respect to the inner region. The reason for the warp is unclear, but the position angle points toward the smaller companion galaxy, UGC 8313.

The distance to M63, based upon the luminosity-distance measurement is 8.99 Mpc. The radial velocity relative to the Local Group yields an estimate of 4.65 Mpc. Estimates based on the Tully–Fisher relation range over 5.0 –. The tip of the red-giant branch technique gives a distance of 8.87 ±. M63 is part of the M51 Group, a group of galaxies that also includes M51 (the 'Whirlpool Galaxy').

In 1971, a supernova with a magnitude of 11.8 appeared in one of the arms. It was discovered on May 24 and reached peak light around May 26. The spectrum of this, SN 1971 I, is consistent with a supernova of type I. However, the spectroscopic behavior appeared anomalous.