Messier 100
Galaxy in the constellation Coma Berenices
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Messier 100 (also known as NGC 4321 or the Mirror Galaxy) is a grand design intermediate spiral galaxy in the constellation of Coma Berenices.[5] It is one of the brightest and largest galaxies in the Virgo Cluster and is approximately 55 million light-years[3] from our galaxy, about 166,000 light-years in diameter. It was discovered by Pierre Méchain in 1781[a] and 29 days later seen again and entered by Charles Messier in his catalogue "of nebulae and star clusters".[6][7] It was one of the first spiral galaxies to be discovered,[7] and was listed as one of fourteen spiral nebulae by Lord William Parsons of Rosse in 1850. NGC 4323 and NGC 4328 are satellite galaxies of M100; the former is connected with it by a bridge of luminous matter.[8][9]
| Messier 100 | |
|---|---|
Galaxy Messier 100 imaged by ESO, revealing complex spiral arm structure | |
| Observation data (J2000 epoch) | |
| Constellation | Coma Berenices[1] |
| Right ascension | 12h 22m 54.8616s[2] |
| Declination | +15° 49′ 17.886″[2] |
| Redshift | 0.005240[2] |
| Heliocentric radial velocity | 1,571±1 km/s[2] |
| Distance | 55 Mly[3] |
| Group or cluster | Virgo Cluster |
| Apparent magnitude (V) | 9.3[4] |
| Characteristics | |
| Type | SAB(s)bc[2] |
| Size | ~166,100 ly (50.93 kpc) (estimated)[2] |
| Apparent size (V) | 7.4′ × 6.3′[2] |
| Other designations | |
| HOLM 387A, IRAS 12204+1605, NGC 4321, UGC 7450, MCG +03-32-015, PGC 40153, CGCG 099-030 | |
Early observations
After the discovery of M100 by Méchain, Charles Messier made observations of the galaxy depicting it as a nebula without a star. He pointed out that it was difficult to recognize the nebula because of its faintness.[7] William Herschel was able to identify a bright cluster of stars within the "nebula" during his observations.[7] His son John expanded the findings in 1833. With the advent of better telescopes, John Herschel was able to see a round, brighter galaxy; however, he also mentioned that it was barely visible through clouds. William Henry Smyth extended the studies of M100, detailing it as a pearly white nebula and pointing out diffuse spots.[7]
Star formation
Messier 100 is considered a starburst galaxy[10] with the strongest star formation activity concentrated in its center, within a ring – actually two tightly wound spiral arms attached to a small nuclear bar of radius: one thousand parsecs[11] – where star formation has been taking place for at least 500 million years in separate bursts.[12]
Supernovae
Seven supernovae have been identified in M100:[5]
- On 17 March 1901 Heber Curtis discovered SN 1901B (Type I, mag. 15.6),[13][5][14] at 110"W and 4"N from the galaxy's nucleus.[15]
- Heber Curtis discovered SN 1914A (type unknown, mag. 15.7)[5][16] on 2 March 1914, at 24"E and 111"S from the galaxy's nucleus.[13][15]
- Milton Humason, with observations from early to mid 1960,[b] discovered SN 1959E (Type I, mag. 17.5),[5][17] located 58"E and 21"S from the galaxy's nucleus.[18]
- On 15 April 1979, amateur astronomer Gus Johnson discovered SN 1979C, the first Type II supernova found in the M100 galaxy. However, the star faded quickly, and later observations from x-ray to radio wavelengths revealed its remnant.[5][19][20]
- SN 2006X (Type Ia, mag. 15.3) was discovered by Shoji Suzuki and Marco Migliardi on 7 February 2006, two weeks before fading to magnitude 17.[5][21][22][23]
- Jaroslaw Grzegorzek discovered SN 2019ehk (Type Ib, mag. 16.5) on 29 April 2019. The supernova reached a peak magnitude of approximately 15.8.[24]
- SN 2020oi (Type Ic, mag. 17.28) was discovered by Automatic Learning for the Rapid Classification of Events (ALeRCE) on 7 January 2020.[5][25][26]
