Editing Messier 61 (section)

== Properties ==
M61 is one of the largest members of Virgo Cluster, and belongs to a smaller subgroup known as the ''S Cloud''.<ref name="GOLDMine">{{cite web
|title=Galaxy On Line Database Milano Network (GOLDMine)
|url=http://goldmine.mib.infn.it/
|access-date=2012-08-06
|archive-url=https://web.archive.org/web/20120603100014/http://goldmine.mib.infn.it/
|archive-date=2012-06-03
|url-status=dead
}}</ref><ref name="VirgoAtlas">{{cite web
|title=The Virgo Cluster
|url=http://www.atlasoftheuniverse.com/galgrps/vir.html
|access-date=2013-04-06
}}</ref> The [[Galaxy morphological classification|morphological classification]] of SAB(rs)bc<ref name="ned" /> indicates a weakly-barred spiral (SAB) with the suggestion of a ring structure (rs) and moderate to loosely wound spiral arms.<ref name="Class">
{{cite journal
 | last=de Vaucouleurs |first=Gérard
 | title=Revised Classification of 1500 Bright Galaxies
 | journal=Astrophysical Journal Supplement
 | date=April 1963 | volume=8 | page=31
 | doi=10.1086/190084 |bibcode=1963ApJS....8...31D
}}</ref> It has an [[active galactic nucleus]]<ref name="Jiménez-Bailón2003">
{{cite journal
|last1=Jiménez-Bailón |first1=E. |last2=Santos-Lleó |first2=M. |last3=Mas-Hesse |first3=J. M. |last4=Guainazzi |first4=M. |last5=Colina |first5=L. |last6=Cerviño |first6=M. |last7=González Delgado |first7=Rosa M.
|date=2003
|title=Nuclear Activity and Massive Star Formation in the Low-Luminosity Active Galactic Nucleus NGC 4303: Chandra X-Ray Observations
|journal=[[The Astrophysical Journal]]
|volume=593 |issue=1 |pages=127–141
|doi=10.1086/376554
|bibcode=2003ApJ...593..127J
|arxiv=astro-ph/0304465
|s2cid=12969809 }}</ref> and is classified as a [[starburst galaxy]] containing a [[Super star cluster|massive]] [[nuclear star cluster]] with an estimated mass of 10<sup>5</sup> [[solar mass]]es and an age of 4 million years,<ref name="Colina2002">{{cite journal |last1=Colina |first1=L. |last2=Gonzalez Delgado |first2=R. |last3=Mas-Hesse|first3=J. Miguel |last4=Leitherer |first4=C. |last5=Jimenez Bailon |first5=E.
|date=2002
|title=Detection of a Super-Star Cluster as the Ionizing Source in the Low-Luminosity Active Galactic Nucleus NGC 4303
|journal=[[The Astrophysical Journal]]
|volume=579 |issue=2 |pages=545–553
|doi=10.1086/342839
|bibcode=2002ApJ...579..545C|doi-access=free |hdl=10261/191615 |hdl-access=free }}</ref> as well as a central candidate [[supermassive black hole]] weighing around {{solar mass|5×10<sup>6</sup>}} solar masses.<ref name="Pastorini2007">{{cite journal |last1=Pastorini |first1=G. |last2=Marconi |first2=A. |last3=Capetti |first3=A. |last4=Axon |first4=D. J. |last5=Alonso-Herrero |first5=A.|author5-link=Almudena Alonso-Herrero |last6=Atkinson |first6=J. |last7=Batcheldor |first7=D. |last8=Carollo |first8=C. M. | author-link8 = C. Marcella Carollo|last9=Collett |first9=J. |last10=Dressel |first10=L. |last11=Hughes |first11=M. A. |last12=Macchetto |first12=D. |last13=Maciejewski |first13=W. |last14=Sparks |first14=W. |last15=van der Marel |first15=R.
|date=2007
|title=Supermassive black holes in the Sbc spiral galaxies NGC 3310, NGC 4303 and NGC 4258
|journal=[[Astronomy and Astrophysics]]
|volume=469 |issue=2 |pages=405–423
|doi=10.1051/0004-6361:20066784
|bibcode=2007A&A...469..405P
|arxiv=astro-ph/0703149|s2cid=849621 }}</ref>
It cohabits with an older massive star cluster as well as a likely older starburst.<ref name=Colina2002/> Evidence of significant star formation and active bright [[nebula]]e appears across M61's disk.<ref name="Koopmann2004">
{{cite journal
|last1=Koopmann |first1=R. |last2=Kenney |first2=J. D. P.
|date=2004
|title=Hα Morphologies and Environmental Effects in Virgo Cluster Spiral Galaxies
|journal=The Astrophysical Journal
|volume=613 |issue=2 |pages=866–885
|bibcode=2004ApJ...613..866K
|doi=10.1086/423191
|arxiv=astro-ph/0406243
|s2cid=17519217 }}</ref> Unlike most [[Hubble classification|late-type spiral galaxies]] within the Virgo Cluster, M61 shows an unusual abundance of [[neutral hydrogen]] (H I).<ref name="Kenney1986">
{{cite journal
|last1=Kenney |first1=J. D.
|last2=Young |first2=J. S.
|date=1986
|title=CO in H I-deficient Virgo cluster spiral galaxies
|journal=[[The Astrophysical Journal Letters]]
|volume=301 |pages=L13–L17
|doi=10.1086/184614
|bibcode=1986ApJ...301L..13K|doi-access=free
}}</ref>