Messier 9

Messier 9 is a small, bright globular cluster and was discovered in 1764 together with M 10, M 12 and M 14 within a few nights. Messier noted: «Nebula, without star, in the right leg of Ophiuchus; it is round and its light faint.» ^[281]

M 9 is the smallest cluster of this quartet. The most striking feature is its slightly oval shape and a small curved chain of six stars southwest of the center (see Fig. 1). At the moment it is not known to the author whether this star chain belongs to M 9 or is only in the foreground. M 9 is relatively close to the central bulge of the Milky Way system. The calculated distance is given as about 7500 light years. For comparison: the sun is around 26'000 light years away from the galactic center. The diameter of M 9 is around 60 light years and the total luminosity is estimated to be 60'000 times that of the sun, if one can assume that around half of the light is absorbed by interstellar matter in between. Strong absorption in the north and west suggests that the light is weakened by at least about one magnitude. Not surprising, since the sharply delimited dark cloud Barnard 64, which appears to be part of a larger complex of interstellar matter, is located close to M 9 in a westerly direction. The globular cluster moves away from us at a radial speed of about 225 km/s. ^[4]

Barnard 64

In 1919, Edward. E. Barnard discovered a cometary dark cloud west of M 9 in one of his photographs and listed it as B 64 in his publication «On the Dark Markings of the Sky». ^[239]