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] |
Group or cluster | Virgo Cluster |
Apparent magnitude (V) | 9.3[4] |
Characteristics | |
Type | SAB(s)bc[2] |
Size | 107,000 ly (diameter) |
Apparent size (V) | 7′.4 × 6′.3[2] |
Other designations | |
NGC 4321 |
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, its diameter being 107,000 light years, and being about 60% as large. 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]
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.
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.
Seven supernovae have been identified in M100.[5]