Globular Cluster Messier 12

Messier 12
Messier 12: Image taken with the Hubble Space Telescope. © ESA/Hubble & NASA [215]

History

In May 1764 Charles Messier discovered another globular cluster, Messier 12, only 3.4° north of M 10, which appears somewhat larger but darker. As was the case with most globular clusters, Messier and Bode initially believed that these «nebulae» did not contain any single stars. About two decades later Sir William Herschel recognized the true nature of M 12 as a grouping of thousands upon thousands of single stars.

Physical Properties

The integrated spectral type of all stars in this globular cluster is F7. Published distances from M 12 vary from 16'000 to 24'000 light years. Presumably it is at the same distance as M 10. The true distance of these two clusters would then be about 2000 light years. M 12 approaches with a radial speed of only about 17 km/s. [4]

«Revised NGC/IC», «Historic NGC/IC», Version 2022-09-01, © Dr. Wolfgang Steinicke [277]
DesignationNGC 6218
TypeGCL (IX)
Right Ascension16h 47m 14.5s
Declination-01° 56' 50"
Diameter16 arcmin
Visual magnitude6.1 mag
Metric Distance4.800 Mpc
Dreyer Description!! globular, vB, vL, iR, gmbM, rrr, st 10…
Identification, RemarksM 12, GCL 46

Finder Chart

The globular cluster Messier 12 is located in the constellation Serpent Bearer (Ophiuchus) approximately where the imaginary connecting lines between the stars κ - ζ Ophiuchi and β - Yed Prior (δ Ophiuchi) cross.

Ophiuchus: Messier 12
Chart Messier 12
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)