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Messier 100
Galaxy in the constellation Coma Berenices From Wikipedia, the free encyclopedia
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Messier 100 (also known as NGC 4321 or the Mirror Galaxy) is a grand design intermediate spiral galaxy in the southern part of the mildly northern 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]
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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[7] to recognize the nebula because of its faintness. William Herschel was able to identify a bright cluster of stars[7] within the "nebula" during his observations. 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[7] extended the studies of M100, detailing it as a pearly white nebula and pointing out diffuse spots.
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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]
As usual on spiral galaxies of the Virgo Cluster, in the rest of the disk both star formation[13] and neutral hydrogen, of which M100 is deficient compared to isolated spiral galaxies of similar Hubble type,[14] are truncated within the galaxy's disk, which is caused by interactions with the intracluster medium of Virgo.
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Supernovae
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Seven supernovae have been identified in M100:[5]
- On 17 March 1901 Heber Curtis discovered SN 1901B (Type I, mag. 15.6),[15][5][16] at 110"W and 4"N from the galaxy's nucleus.[17]
- Heber Curtis discovered SN 1914A (type unknown, mag. 15.7)[5][18] on 2 March 1914, at 24"E and 111"S from the galaxy's nucleus.[15][17]
- Milton Humason, with observations from early to mid 1960,[b] discovered SN 1959E (Type I, mag. 17.5),[5][19] located 58"E and 21"S from the galaxy's nucleus.[20]
- 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][21][22]
- 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][23][24][25]
- Jaroslaw Grzegorzek discovered SN 2019ehk (Type Ib, mag. 16.5) on 29 April 2019. The supernova reached a peak magnitude of approximately 15.8.[26]
- SN 2020oi (Type Ic, mag. 17.28) was discovered by Automatic Learning for the Rapid Classification of Events (ALeRCE) on 7 January 2020.[5][27][28]
See also
References and footnotes
External links
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