Messier 100
A grand design spiral galaxy in the Virgo Cluster.
Messier 100 (NGC 4321, also called the Mirror Galaxy) is a grand design intermediate spiral located in Coma Berenices. Among the brightest and largest members of the Virgo Cluster, it lies about 55 million light-years from the Milky Way and spans roughly 166,000 light-years across. It was discovered by Pierre Méchain in 1781 and 29 days later seen again and entered by Charles Messier in his catalogue "of nebulae and star clusters". It was also one of the earliest spiral galaxies recognized, listed among fourteen spiral nebulae by Lord William Parsons of Rosse in 1850. Two satellite galaxies, NGC 4323 and NGC 4328, orbit M100, with a luminous bridge connecting the former to the main galaxy. Early observers found M100 challenging. Messier described it as a starless nebula, noting its faintness made it hard to identify. William Herschel later detected a bright star cluster within it, and his son John Herschel, using better telescopes in 1833, saw a round, brighter galaxy—though he remarked it was barely visible through clouds. William Henry Smyth extended these studies, calling it a pearly white nebula with diffuse spots. M100 is a starburst galaxy, with its most intense star formation occurring in a central ring—actually two tightly wound spiral arms attached to a small nuclear bar about one thousand parsecs across. This activity has proceeded in separate bursts for at least 500 million years. Seven supernovae have been recorded in M100. Heber Curtis discovered SN 1901B (Type I, magnitude 15.6) on March 17, 1901, and SN 1914A (type unknown, magnitude 15.7) on March 2, 1914. Milton Humason found SN 1959E (Type I, magnitude 17.5) in early to mid-1960. Amateur astronomer Gus Johnson spotted SN 1979C on April 15, 1979—the first Type II supernova in M100—though it faded quickly, leaving a remnant detected from X-ray to radio wavelengths. SN 2006X (Type Ia, magnitude 15.3) was discovered by Shoji Suzuki and Marco Migliardi on February 7, 2006, dimming to magnitude 17 two weeks later. Jaroslaw Grzegorzek found SN 2019ehk (Type Ib, magnitude 16.5) on April 29, 2019, peaking at about magnitude 15.8. SN 2020oi (Type Ic, magnitude 17.28) was detected by the ALeRCE system on January 7, 2020.
Quick Facts
- Constellation Name
- Coma Berenicessinnott1988
- Epoch
- J2000
- Ra
- 12 · 22 · 54.8616
- Dec
- +15 · 49 · 17.886
- Dist Ly
- 55 Mly
- Z
- 0.005240
- Appmag V
- 9.3seds
- Stars
- 400 billion (4×10 / 11 / )
- Group Cluster
- Virgo Cluster
Facts from the source article.
Lore & Background
After the discovery of M100 by Méchain, Charles Messier made observations of the galaxy depicting it as a nebula without a star, noting it was difficult to recognize because of its faintness. William Herschel identified a bright cluster of stars within the 'nebula,' and his son John expanded the findings in 1833, seeing a round, brighter galaxy but mentioning it was barely visible through clouds. William Henry Smyth extended the studies, detailing it as a pearly white nebula and pointing out diffuse spots. Messier 100 is considered a starburst galaxy 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—where star formation has been taking place for at least 500 million years in separate bursts. It has two satellite galaxies: NGC 4323, connected by a bridge of luminous matter, and NGC 4328. Seven supernovae have been identified in M100, including SN 1901B discovered by Heber Curtis, SN 1914A also by Curtis, SN 1959E by Milton Humason, SN 1979C by amateur astronomer Gus Johnson, SN 2006X by Shoji Suzuki and Marco Migliardi, SN 2019ehk by Jaroslaw Grzegorzek, and SN 2020oi by ALeRCE.
Reader's Guide
Messier 100 holds significance as one of the first spiral galaxies to be discovered, listed as one of fourteen spiral nebulae by Lord William Parsons of Rosse in 1850. Its early observations by Méchain, Messier, the Herschels, and Smyth contributed to the evolving understanding of nebulae and galaxies. The galaxy's status as a starburst galaxy with a central ring of intense star formation highlights its role in studying stellar birth processes. The detection of seven supernovae over more than a century, including the first Type II supernova found in M100 (SN 1979C), provides a rich dataset for supernova research. Its satellite galaxies, particularly NGC 4323 connected by a luminous bridge, offer insights into galactic interactions. As a bright member of the Virgo Cluster, M100 remains a key target for amateur and professional astronomers alike.
Did You Know?
- M100 is also known as NGC 4321 or the Mirror Galaxy.
- Seven supernovae have been identified in M100, including SN 1979C, the first Type II supernova found in this galaxy.
- NGC 4323, a satellite galaxy of M100, is connected to it by a bridge of luminous matter.
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