Object of the Week August 25, 2013 - Abell 64, the “planetary - galaxy”
Abell 64 (= PNG 044.2-09.4; CGCG 397-005, PGC 63630)
Aquila
RA: 19 45 35
Dec: +05 33 52
Mag: 15,3 NED
Size: 0,8’x0,5’
Distance: 39Mpc
Type: G
The first reference of our OOTW was given by Zwicky in 1965, when he and his colleagues catalogued thousands of galaxies in the CGCG (Catalogue of Galaxies and of Clusters of Galaxies) catalogue. The raw data did not give any velocity/redshift and so no idea of the distance and the “real type” of the object.
Second, but the most famous reference of our “PN Glx” was given by Mr. George Abell himself in the year 1966. He numbered the nebula as 64 in his list of 86 new indentified objects from the plates of the Palomar Sky Survey. He classed all objects as “planetary nebula” and concludes a distance of 1700pc for this new object.
Later, the nebula found entry in the Perek-Kohoutek (PK) Catalogue of Galactic Planetary Nebula, later in the following Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (PNG).
1996 Marzke, Huchra, Geller presented redshifts for 2020 galaxies selected from the CGCG and listed a redshift of 0.010194 (39Mpc) which indicate this object as a normal galaxy.
Indeed, the classification of Abell was a misclassification and Abell 64 aka CGCG 397-5 now counts as a galaxy. The typical misclassification is visible perfectly even in smaller telescopes because of a negative reaction of any nebula filter and a missing of a central star.
The galaxy is visible from the 8”-10” telescope class as a very faint spot of light which disappear when using a filter. From 16” the brightest knot “false central star” is visible and with 24”+ the galaxy showed many spots within the square body. This is the real challenge, to pick up the spots within the galaxy.
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