Messier 100

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.<ref name="seds1"> Template:Cite web</ref> It is one of the brightest and largest galaxies in the Virgo Cluster and is approximately 55 million light-years<ref name="distance"> Template:Cite web</ref> from our galaxy, about 166,000 light-years in diameter. It was discovered by Pierre Méchain in 1781Template:Efn and 29 days later seen again and entered by Charles Messier in his catalogue "of nebulae and star clusters".<ref> Template:Cite web</ref><ref name="seds2"> Template:Cite web</ref> It was one of the first spiral galaxies to be discovered,<ref name="seds2" /> 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.<ref> Template:Cite journal</ref><ref> Template:Cite simbad</ref>

Early observations

File:Widefield View of M100.png

This is a widefield view of the galaxy, M100, directly left of the center of the picture - captured with an amateur telescope in 2025.

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<ref name="seds2" /> to recognize the nebula because of its faintness. William Herschel was able to identify a bright cluster of stars<ref name="seds2" /> 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<ref name="seds2" /> extended the studies of M100, detailing it as a pearly white nebula and pointing out diffuse spots.

Star formation

Messier 100 is considered a starburst galaxy<ref> Template:Cite journal</ref> 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<ref> Template:Cite journal</ref> – where star formation has been taking place for at least 500 million years in separate bursts.<ref> Template:Cite journal</ref>

As usual on spiral galaxies of the Virgo Cluster, in the rest of the disk both star formation<ref name="koopmannkenney2004"> Template:Cite journal</ref> and neutral hydrogen, of which M100 is deficient compared to isolated spiral galaxies of similar Hubble type,<ref name=Chung2009> Template:Cite journal</ref> are truncated within the galaxy's disk, which is caused by interactions with the intracluster medium of Virgo.

Supernovae

File:Noirlab2019b.jpg

Supernova SN 2019ehk in M100 (Hubble)

Seven supernovae have been identified in M100:<ref name="seds1" />

• On 17 March 1901 Heber Curtis discovered SN 1901B (type I, mag. 15.6),<ref name="Ritchie">Template:Cite journal</ref><ref name="seds1" /><ref>

Template:Cite simbad</ref> at 110"W and 4"N from the galaxy's nucleus.<ref name=Curtis>Template:Cite journal</ref>

• Heber Curtis discovered SN 1914A (type unknown, mag. 15.7)<ref name="seds1" /><ref>

Template:Cite simbad</ref> on 2 March 1914, at 24"E and 111"S from the galaxy's nucleus.<ref name=Ritchie /><ref name=Curtis />

• Milton Humason, with observations from early to mid 1960,Template:Efn discovered SN 1959E (type I, mag. 17.5),<ref name="seds1" /><ref>

Template:Cite simbad</ref> located 58"E and 21"S from the galaxy's nucleus.<ref>Template:Cite journal</ref>

• 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.<ref name="seds1" /><ref>

Template:Cite simbad</ref><ref>Template:Cite journal</ref>

• 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.<ref name="seds1" /><ref>

Template:Cite simbad</ref><ref>Template:Cite journal</ref><ref>Template:Cite web</ref>

• Jaroslaw Grzegorzek discovered SN 2019ehk ([[Type Ib and Ic supernovae|typeTemplate:NbspIb]], mag. 16.5) on 29 April 2019. The supernova reached a peak magnitude of approximately 15.8.<ref>Template:Cite web</ref>
• SN 2020oi ([[Type Ib and Ic supernovae|typeTemplate:NbspIc]], mag. 17.28) was discovered by Automatic Learning for the Rapid Classification of Events (ALeRCE) on 7 January 2020.<ref name="seds1" /><ref>

Template:Cite simbad</ref><ref>Template:Cite web</ref>

See also

• List of Messier objects

External links

• SEDS: Spiral Galaxy 100
• Template:Sky-Map.org
• ESA/Hubble Messier 100
• NASA Astronomy Picture of the Day