A 30 minute exposure thru Kopernik's
20-inch R-C Cassegrain telescope.
A 30 minute exposure thru Kopernik's
20-inch R-C Cassegrain telescope.
The field of view is about 13x16 arc minutes with North at the Top.
International Astronomical Union Circular 7335 reported the discovery on December 17th 1999 of a supernova in M-61 by amateur astronomer Alessandro Dimai, of Cortina, Italy. It was magnitude 16.0 at discovery. Later observations show that it is a Type II supernova discovered before it had reached its peak brightness and that the ejected material was expanding at 5,300 km per second. Previous supernovae in M61 were 1926a, 1961i, and 1964f.
The Kopernik image shown here was taken at 5:50 UT (1 am local time) on April 1st, 2000, using our 20 inch telescope. The supernova is about 15.5 magnitude in our image.
B. Oriani, May 5th, 1779: "Very pale looking, exactly like the comet."
C. Messier, May 11th, 1779: "A nebula, very faint and difficult to distinguish. M. Messier mistook this nebula for the comet of 1779 on the 5th, 6th, and 11th of May. On the 11th he found it was not a comet but a nebula which was on its path and in the same part of the sky."
Italian astronomer B. Oriani discovered M-61 in May 1779, while observing the comet of that year. Messier found it a few nights later and at first mistook it for the comet.
M-61 is a nearly face-on spiral galaxy with a small bar found in the Constellation of Virgo. It is probably a part of the Coma/Virgo galaxy cluster. Various sources state that it has a distance of about 40 million light years, with a diameter of 60,000 light years. M-61 may belong to the class of galaxies with active nuclei known as Seyfert galaxies. (see also M-77) Filippenko & Sargent (1985) showed that the nuclear spectrum is that of a H II region, each line, however, having a broad base suggesting the presence of a faint Seyfert 2 nucleus. Later observations seem to show that the H II region forms a ring around the nucleus and that prodigious star formation is occurring in the galaxy. A rather unusual effect is seen in the spiral structure of this galaxy. The arms show several sudden changes of direction at sharp angles, producing an over-all polygonal structure, and there is an exceptionally bright and thick star cloud in the arm on the north edge of the system. Supernovae were recorded in M-61 in 1926, 1961, and 1964, and 1999.
Quote from A. Sandage's The Hubble Atlas of Galaxies, 1965:
The galaxy has some characteristics of a barred spiral...... Two thin dust lanes (width about 150 parsecs) wind out through the pseudo bar to the inside of the beginning of the two main luminous arms. Many faint arms are present on the outside of the two bright ones. The many knots in the brighter arms are undoubtedly HII regions.
George Normandin, KAS
April 3rd, 2000
Revised: March 19, 2002 and May 31, 2007