NGC 5866 (M102 ?)

Right Ascension	15 : 06.5 (h:m)
Declination	+55 : 46 (deg:m)
Distance	40000 (kly)
Visual Brightness	9.9 (mag)
Apparent Dimension	5.2x2.3 (arc min)

NGC 5866 is a beautiful lenticular galaxy of visual magnitude 10.0 or 9.6 (the first value from Sky Catalogue 2000.0, the latter is an estimate by Don Machholz). It is seen almost exactly edge-on. The fine dark dust lane shows up nice in this image; it is tilted by about 2 degrees against the galaxy's symmetry plane. Longer exposures overexpose the dust lane so that this galaxy was often misclassified as elliptical of type E6 instead of the correct type S0_3 (some sources have even classified it as Sa), see e.g. the comparison of 2 images in Sandage's Hubble Atlas of Galaxies, plate 6. They show however an extended system of globular clusters. See also the Digital Sky Survey image.

This galaxy is situated in the northern constellation Draco at RA 15h 06.5, Dec +55d 46' (2000.0). It is the brightest of a remarkable group of galaxies (the NGC 5866 group), lying roughly 40 million light-years distant (R. Brent Tully's Nearby Galaxies Catalog has the slightly larger value of about 50 million light-years), which also contains the big bright edge-on spiral NGC 5907 (type Sb+, 10.4 mag vis), the fainter galaxy NGC 5879 (Sb, 11.5), and more very faint galaxies (NGCs 5866A and 5866B, 5862, 5905, 5908 and IC 1099). From the dynamics of that group, E.M. and G.R. Burbidge (ApJ 131, p. 224-226, 1960) have estimated NGC 5866's mass to be about 1 trillion solar masses, so it is a considerably massive galaxy. The 5.2' diameter of NGC 5866 correspondes to about 60,000 light-years, its globular cluster halo extends more far outward. No supernovae have been discovered in this galaxy yet.

NGC 5866 is possibly M102, i.e. it is plausible that Pierre Mechain had found and described this object (but he later disclaimed). There is some evidence that Charles Messier may have observed this object when measuring the position he added to entry No. 102 in his personal copy, but this subject is still somewhat dubious and therefore controversial. If it should be true that neither Mechain nor Messier have observed NGC 5866, it was probably first seen by William Herschel (or perhaps by Caroline Herschel) in the mid or late 1780s; it bears Herschel's number H I.215 (Admiral Smyth writes it was discovered in March, 1789).

Our image of NGC 5866 was provided by Stephan. It was taken by Bernd Koch and Stefan Korth, on 12 March 1995 at 1:09 UT with a Celestron 14 at f=4.060mm, located at the Sternwarte Aufderhö.he near Solingen, Germany. The camera was a Starlight XPress, exposure time 5m 28s. Image processing was done with PIXWIN and Corel PhotoPaint by the authors.

More images of NGC 5866