Globular Cluster Messier 54

Messier 55
Messier 55: Image taken with the Hubble Space Telescope. © ESA/Hubble & NASA [215]

History

The globular cluster M 54 was discovered by Charles Messier on 24 July 1778, and NGC 6715 was later included in J. L. E. Dreyer's 1888 «New General Catalogue of Nebulae and Clusters of Stars». Messier described his 54th discovery as «a very bright nebula, discovered in Sagittarius, bright in the center and containing no star as seen with a 3.5 feet achromatic telescope [focal length]». Probably John Herschel was the first to break up the globular cluster into single stars in 1834. [4]

Physical Properties

M 54 is the second most massive globular cluster. Distance measurements result in a distance of 88'100 to 97'800 light years [145]. The globular cluster is therefore very far from the Milky Way. At first it was assumed that it belonged to the Milky Way, but in 1994 it became clear that M 54 actually belongs to the neighboring Sagittarius Dwarf Galaxy (Sgr dSph, Sag DEG). This dwarf galaxy is in a spiral, polar orbit around the center of the Milky Way and is currently about 50'000 light years away from it. Due to the force of gravity, the Milky Way will incorporate this dwarf galaxy including globular clusters. From our perspective, M 54 lies exactly in the center of this dwarf galaxy, which is why it was first suspected that its core was there. However, a study showed that both have different stellar populations and therefore must have originated independently of each other. They found each other later through gravity. [215, 278]

Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
DesignationNGC 6715
TypeGCL (III)
Right Ascension18h 55m 03.3s
Declination-30° 28' 40"
Diameter12 arcmin
Visual magnitude7.7 mag
Metric Distance26.500 kpc
Dreyer Descriptionglobular, vB, L, R, g, smbM, rrr, st 15
Identification, RemarksM 54, GCL 104, ESO 458-SC8

Finder Chart

The globular cluster is located in the southeast corner of the teapot in the constellation Sagittarius, about 1.75° WSW from the double star Ascella (ζ Sagittarii). The best time to observe is June to August.

Chart Globular Cluster Messier 54
Globular Cluster Messier 54 in constellation Sagittarius. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

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
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
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)
278«The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy» Michael H. Siegel, Aaron Dotter, Steven R. Majewski, Ata Sarajedini, Brian Chaboyer, David L. Nidever, Jay Anderson, Antonio Marín-Franch, Alfred Rosenberg, Luigi R. Bedin, Antonio Aparicio, Ivan King, Giampaolo Piotto, I. Neill Reid;; DOI:10.1086/522003