Messier 105 - Galaxy Group
In the constellation Leo there are some nice galaxy groups apart from the well known Leo triplet. One of them is the group around Messier 105,
which consists of 3 galaxies: Messier 105, NGC 3384 and NGC 3389.
While M105 and NGC 3384 are 36 million lightyears away from Earth, NGC 3389 is located in the background with a distance of about 55 million
lightyears and therefore doesn't belong to the group - so this galaxy is also not gravitationally bound and lies just in the same direction as the other
two galaxies.
Messier 105 belongs to the group of elliptical galaxies of Hubble type "E1" and was discovered in March 1781 by Pierre Méchain. It has an
apparent magnitude of 9.5mag and a size of 5.3'x4.8'. The absolute magnitude is M= -20.7mag, which corresponds to a luminosity of 17 billion
suns. The galaxy has a diameter of about 55,000 light years and is a nearly perfect ellipse with no fine structure. In the center there is a black hole
with 200 million solar masses. It is surrounded by a rapidly rotating ring structure. Like NGC 3384, Messier 105 is surrounded by a ring of neutral
hydrogen with a total mass of 1.8 billion solar masses.
NGC 3384 was discovered only 3 years after Messier 105, namely in 1784 by F.W. Herschel. The apparent magnitude is 9.9mag and the size is
5.4'x2.7'. It is either an elliptical galaxy of type E7 or a lenticular galaxy of type SB0 with a diameter of 55,000 light years. 80% of the stars in the
central region are older than 1 billion years and directly in the center there is a SMBH with 14...17 million solar masses.
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This wonderful galaxy trio appears very bright in my 20" f/3 and all three galaxies are easily visible. NGC 3389 is much fainter than the other two
galaxies.
Of course, details in elliptical galaxies are always a problem, because these galaxies do not really have structures that can be observed. At most, you
can increase the magnification and see if there is a stellar core in the center. Of course, these are not real stars, it's just the combined light of millions
of stars all concentrated in a very small area of space.
So if you want to see something else than only the Leo triplet, you may want to visit the group around Messier 105.
