Messier 61

Right Ascension	12 : 21.9 (h:m)
Declination	+04 : 28 (deg:m)
Distance	60000 (kly)
Visual Brightness	9.7 (mag)
Apparent Dimension	6x5.5 (arc min)

Discovered 1779 by Barnabus Oriani.

Messier 61 (M61, NGC 4303) is a considerable spiral galaxy in the southernmost part of the Virgo Cluster of Galaxies.

M61 was discovered by Barnabus Oriani on May 5, 1779 when following the comet of that year, 6 days before Charles Messier's discovery, who had seen it on the same day as Oriani but mistaken it for the comet. Messier mistook it for two nights more, until he realized that it did not move. As for a small number of others, this object was assigned an own number, H I.139, by William Herschel, who normally avoided to give own numbers to Messier's objects, when he observed and cataloged it on April 17, 1786.

M61 is one of the larger galaxies in the Virgo cluster; its 6 arc minutes of diameter correspond to about 100,000 light years, similar to the diameter of the Milky Way galaxy. Its 10th magnitude corresponds to an absolute magnitude of -21.2.

Seven supernovae have been observed in M61 (one of them uncertain):

• 1926A (12.8 mag) was discovered by Wolf and Reinmuth,
• 1961I (mag 13, Humason),
• 1964F (mag 12, Rosino),
• 1999gn (13.4 mag, Dimai),
• 2006ov (14.8 mag, Itagaki),
• 2008in (14.3 mag, Itagaki), and
• 2014dt (13.2 mag, Itagaki).

One further object had been suspected to be a supernova in M61: PSN J12215513+0428169, discovered at 19.0 mag by Lick Observatory Supernova Search (LOSS) in March 2014, but it remained weak and may more probably have been an ordinary Nova in M61.

With its seventh supernovae flashing up, M61 has taken over the current record mark which had been previously hold by M83 with 6, to lead in the statistics of Messier galaxies. At the time of this writing (December 2014), it is two SNe behind the overall record holder, NGC 6946.

NGC Online data for M61

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Hartmut Frommert
Christine Kronberg
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Last Modification: December 9, 2014