Globular Cluster Messier 9

Messier 9
Messier 9: Image taken by Hubble Space Telescope [215]

Object Description

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. 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 B 62, which appears to be part of a larger complex of interstellar matter, is located close to M 9 in a south-westerly direction. The globular cluster moves away from us at a radial speed of about 225 km/s. [4]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationNGC 6333
TypeGCL (VIII)
Right Ascension17h 19m 11.8s
Declination-18° 30' 57"
Diameter12.00 arcmin
Visual magnitude7.8 mag
Dreyer Descriptionglobular, B, L, R, eCM, rrr, st 14
IdentificationM 9, GCL 60, ESO 587-SC5

Finder Chart

The globular cluster Messier 9 is located in the constellation Serpent Bearer (Ophiuchus), roughly in the middle between the 2.43 mag bright star Sabik (η Ophiuchi) and the 4.39 mag bright star ξ Ophiuchi. It is best seen between May and July.

Chart Messier 9
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

References

4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
215Explore - The Night Sky | Hubble’s Messier Catalog; nasa.gov/content/goddard/hubble-s-messier-catalog (2020-12-31)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)