| Messier 100 | |
|---|---|
| Observation data (J2000 epoch) | |
| Constellation | Coma Berenices[1] |
| Right ascension | 12h 22m 54.9s[2] |
| Declination | +15° 49′ 21″[2] |
| Redshift | 1571 ± 1 km/s[2] |
| Distance | 55 Mly[3] |
| Type | SAB(s)bc[2] |
| Apparent dimensions (V) | 7′.4 × 6′.3[2] |
| Apparent magnitude (V) | 10.1[2] |
| Other designations | |
| NGC 4321 | |
| See also: Galaxy, List of galaxies | |
Messier 100 (also known as NGC 4321) is an example of a grand design spiral galaxy[4] located within the southern part of constellation Coma Berenices. It is one of the brightest galaxies in the Virgo cluster, approximately 55 million light-years[3] distant from Earth and has a diameter of 160,000 light years. It was discovered by Pierre Méchain on March 15, 1781 and was subsequently entered in Messier’s catalogue of nebulae and star clusters[5] after Charles Messier[6] made observations of his own on April 13, 1781. The galaxy was one of the first spirals[6] discovered, and was listed as 1 of 14 spiral nebulae by Lord William Parsons of Rosse in 1850. A satellite galaxy[7][8] named NGC 4323 is present within M100.
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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[6] to recognize the nebula because of its faintness. William Herschel was able to identify a bright cluster of stars[6] within the nebula during observations he did before John Herschel 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 but he still indicated that it was faint. William Henry Smyth[6] extended the studies of M100, detailing it as a pearly white nebula and pointing out diffuse spots.
Five supernovae[4] have been identified in the M100 galaxy. In March 1901 the first supernova of M100 was found, SN 1901B,[4][9] a type I supernova found when magnitude 15.6 at a distance from its nucleus. SN 1914A[4][10] was then discovered in February to March 1914; its type was undeterminable but was found when magnitude 15.7 at some distance from the center. Observations of M100 from February 21, 1960 to June 17, 1960 led to the discovery of SN 1959E, another type I supernova,[4][11] with the faintest magnitude, 17.5, among the five found, at 58"E and 21"S from its nucleus. On April 15, 1979, the first type II supernova found in the M100 galaxy was discovered; however the star SN 1979C[4][12] faded quickly; later observations from x-ray to radio wavelengths revealed its remnant. The latest supernova was discovered February 7, 2006; the star SN 2006X[4][13] had a magnitude of 15.3 when discovered two weeks before fading to magnitude +17.
Coordinates: 12h 22m 54.9s, +15° 49′ 21″
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