Messier 63 orM63, also known asNGC 5055 or the seldom-usedSunflower Galaxy,[5] is aspiral galaxy in the northernconstellation ofCanes Venatici with approximately 400 billion stars.[6] M63 was first discovered by the French astronomerPierre Méchain, then later verified by his colleagueCharles Messier on 14 June 1779.[5] The galaxy became listed as object 63 in theMessier Catalogue. In the mid-19th century, Anglo-Irish astronomerLord Rosse identified spiral structures within the galaxy, making this one of the first galaxies in which such structure was identified.[7]
The shape or morphology of this galaxy has aclassification of SAbc,[8] indicating a spiral form with no centralbar feature (SA) and moderate to loosely woundarms (bc). There is a general lack of large-scale continuous spiral structure in visible light, so it is considered aflocculent galaxy. However, when observed in thenear infrared, a symmetric, two-arm structure is seen. Each arm wraps 150° around the galaxy and extends out to 13,000light-years (4,000parsecs) from the nucleus.[9]
M63 is a weaklyactive galaxy with aLINER nucleus – short for 'low-ionization nuclear emission-line region'. This displays as an unresolved source at the galactic nucleus that is cloaked in a diffuseemission. The latter is extended along aposition angle of 110° relative to thenorth celestial pole, and bothsoft X-rays and hydrogen (H-alpha) emission can be observed coming from along nearly the same direction.[10] The existence of asupermassive black hole (SMBH) at the nucleus is uncertain; if it does exist, then the mass is estimated as(8.5±1.9)×108M☉,[11] or around 850 million times the mass of the Sun.
Radio observations at the21-cm hydrogen line show the gaseous disk of M63 extends outward to a radius of 130,000 light-years (40 kiloparsecs), well past the bright optical disk. This gas shows a symmetrical form that is warped in a pronounced manner, starting at a radius of 33,000 light-years (10 kiloparsecs). The form suggests adark 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.[12]
The distance to M63, based upon the luminosity-distance measurement is 29,300,000 light-years (8.99 megaparsecs).[4] Theradial velocity relative to theLocal Group yields an estimate of 15,200,000 light-years (4.65 megaparsecs).[8] Estimates based on theTully–Fisher relation range over 16,000,000–34,000,000 light-years (5.0–10.3 megaparsecs). Thetip of the red-giant branch technique gives a distance of 28,930,000 ± 950,000 light-years (8.87 ± 0.29 megaparsecs).[13] M63 is part of theM51 Group, a group of galaxies that also includesM51 (the 'Whirlpool Galaxy').[14]
Onesupernova has been observed in M63:SN 1971I (TypeIa, mag. 11.8) was discovered by Glenn Jolly on 24 May 1971,[15] and was discovered independently by Roger Clark on 29 May 1971.[16][17][18] It reached peak light around 26 May.[19] While the spectrum was consistent with a supernova of type I, the spectroscopic behavior appeared anomalous.[17]
M63 imaged inUV light by theGALEX satellite. The UV light is produced primarily by young, massive stars, so the UV-bright areas are regions where stars are currently forming.[20] CreditNASA /WikiSky
Messier 63 seen in theinfrared by theSpitzer Space Telescope. The infrared radiation traces the dust within the spiral arms, which does not radiate visible light. A small dust ring can be seen just outside of the galaxy's center.[21]
The Sunflower Galaxy M 63 taken in France by amateur astrophotographer Anthony MICHEL[22]
^Graham, Alister W. (November 2008), "Populating the Galaxy Velocity Dispersion - Supermassive Black Hole Mass Diagram: A Catalogue of (Mbh, σ) Values",Publications of the Astronomical Society of Australia,25 (4):167–175,arXiv:0807.2549,Bibcode:2008PASA...25..167G,doi:10.1071/AS08013,S2CID89905.
^Marsden, Brian G. (25 May 1971)."Circular No. 2330".Central Bureau for Astronomical Telegrams. Smithsonian Astrophysical Observatory,IAU. Retrieved2 August 2025.
^Marsden, Brian G. (8 June 1971)."Circular No. 2333".Central Bureau for Astronomical Telegrams. Smithsonian Astrophysical Observatory,IAU. Retrieved2 August 2025.
^abDeming, Drake; et al. (June 1973), "The Light Curve of Supernova 1971 I",Publications of the Astronomical Society of the Pacific,85 (505): 321,Bibcode:1973PASP...85..321D,doi:10.1086/129462
^"SN1971I".Transient Name Server.IAU. Retrieved2 December 2024.
^Barbon, R.; et al. (1973), "Observations of five supernovae 1970-71",Memorie della Società Astronomia Italiana,44: 65,Bibcode:1973MmSAI..44...65B.
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![M63 imaged in UV light by the GALEX satellite. The UV light is produced primarily by young, massive stars, so the UV-bright areas are regions where stars are currently forming.[20] Credit NASA / WikiSky](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aMessier_63_GALEX_WikiSky.jpg)
![Messier 63 seen in the infrared by the Spitzer Space Telescope. The infrared radiation traces the dust within the spiral arms, which does not radiate visible light. A small dust ring can be seen just outside of the galaxy's center.[21]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aM63_3.6_8.0_24_microns_spitzer.png)
![The Sunflower Galaxy M 63 taken in France by amateur astrophotographer Anthony MICHEL[22]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aM63_Sunflower_Galaxy.png)
