PGC 2725: The Galaxy That Isn't
It is well known that comets are good for surprises. What is less known is that they can fool even experienced scientists. Coincidence revealed that several decades ago, a comet fooled researchers into an object that is still listed in major catalogs today.
As an amateur astronomer, I like to dedicate myself to the extreme objects in the cosmos. I am particularly interested in active galaxies (see SuW 12/2017, p. 68). I use telescopes to visually and photographically monitor the fluctuations in brightness of quasars and BL-Lac objects in order to create light curves and detect any outbursts in brightness at an early stage. I forward the observations to the Federal German Working Group for Variable Stars e. V. (BAV), the American Association of Variable Star Observers (AAVSO) and to the Japanese Variable Star Network (VSNET). In addition, I research the history of selected objects and use the digital photo plate archive of the Landessternwarte Heidelberg (see SuW 3/2010, p. 68).
On November 1st, 2018, there was no exotic galaxy on my agenda, but a periodic comet. The tail star, named 64P/SwiftGehrels, was conveniently positioned this evening in the constellation Andromeda, which pierces high above the horizon in central Europe. I planned to take a short exposure image of the comet with my eight-inch Newtonian telescope (f/3.9). When I looked up the current celestial coordinates and created a finder chart, I became aware of the galaxy PGC2725, which is only about 41 arc minutes northwest of the comet and according to the catalog has an apparent magnitude of 14.5 and could therefore be a worthwhile target…