|Right Ascension||12 : 21.9 (h:m) |Declination||+04 : 28 (deg:m)
|Visual Brightness||9.7 (mag) |Apparent Dimension||6x5.5 (arc
min) Discovered 1779 by Barnabus Oriani. M61 was discovered by
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 2 times 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. Four supernovae have been observed
in M61: 1926A (12.8 mag) was discovered by Wolf and Reinmuth,
1961I (mag 13, Humason), 19