Messier 102 - Spindle Galaxy
For a long time there was some confusion about the 102nd object in the Messier catalog, as it was not entirely clear which galaxy was meant by the term
"Messier 102". It was suspected for a while that it could have been a double observation of Messier 51 or Messier 101. However, based on the available
data, it was finally agreed, that the bright galaxy NGC 5866 is probably the "missing" Messier object. This galaxy was first discovered by P. Mechain in
1781, but also independently by F.W. Herschel some time later in 1788.
The galaxy is located in the constellation "Hunting Dogs" (CVn), is 9.9mag bright and has an apparent size of 4.7'x1.9'. Depending on the source, the distance
is given as around 50 million light-years, but with a large error bar of 10 million light-years.
Messier 102 is a lenticular galaxy of the Hubble Type "S0" with a diameter of around 60,000 light-years. This makes it only half the size of our Milky Way.
Its luminosity corresponds to around 3 billion suns.
Unusual for NGC 5866 is its dust band, which is actually way too large for a lenticular galaxy - because normally the dust lane is only visible in a small area
around the center. Of course, this leaves some room for interpretation: Messier 102 could just as well be a spiral galaxy that we see exactly from the side.
However, the nucleus is a so-called LINER, which means that an emission spectrum of weakly ionized atoms has been found in it.
Messier 102 belongs to a group of three galaxies, which also includes NGC 5879 and the much better-known galaxy NGC 5907. The galaxies lie on the
periphery of the larger groups around Messier 51 and Messier 101.
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Messier 102 offers a beautiful sight in my 20" telescope. Due to its high surface brightness, the galaxy can be magnified well and appears most beautiful at
a magnification of 210...270x.
The lenticular structure with an elongation of 6:1 is clearly visible, the two ends of the galaxy taper to a point. The inner part is a little brighter, but no stellar
core can be seen in the center. Instead, the very thin dust lane can be seen with averted vision and can easily be traced over the entire length of the bulge. The
whole galaxy appears to be surrounded by a very faint halo.
