Release 11.12 ("Hergest Ridge")

Selected: NGC 6121

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Positional Parameters
clusterNGC 6121
nameM 4
RA16 23 35.22
Declination-26 31 32.7
Galactic longitude350.97
Galactic latitude15.97
R sun2.2
R gc5.9
Photometric Parameters
E (B-V)0.35
V HB13.45
Structural Parameters
[Fe / H]-1.16
SpT F8
Color-magnitude diagrams
authorKanatas, I.; Griffiths, W. K.; Dickens, R. J.; Penny, A. J.
titleCCD photometry in the globular cluster M4
journalMNRAS, Volume 272, Issue 2, pp. 265-290 (1995)
CM diagram
Description of NGC 6121

Messier 4 (also known as M4 or NGC 6121) is a globular cluster in the constellation Scorpius. It was discovered by Philippe Loys de Cheseaux in 1746 and catalogued by Charles Messier in 1764.

M4 was the first globular cluster in which individual stars were resolved. M4 is conspicuous in even the smallest of telescopes as a fuzzy ball of light. It is also the one of the easiest globular clusters to find, being located only 1.3 degrees west of the bright star Antares, with both objects being visible in a wide field telescope. Modestly sized telescopes will begin to resolve individual stars of which the brightest in M4 are of apparent magnitude 10.8.

The cluster carries a characteristic "bar" structure across its core, visible in images (including the one below, extending from upper left to lower right) and moderate sized telescopes. The structure consists of 11th magnitude stars and is approximately 2.5' long and was first noted by William Herschel in 1783.

Source: Wikipedia | Notify inaccuracies


Image of the cluster from the Digital Sky Survey

Other Resources
for NGC 6121
ADS "Object Search"
C. Clement variables data
SEDS data
Google Sky
Web Links for this cluster
(2 links in the database at the moment)
Users comments for this cluster
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Selected biblio
Paper n. 1
Lardo, C. et al.
Multiple populations along the asymptotic giant branch of the globular cluster M4
2017, MNRAS, Volume 466, Issue 3, p.3507-3512
(NGC 6121 )
Paper n. 2
Valcarce, A. A. R.; Catelan, M.; Alonso-García, J.; Cortés, C.; De Medeiros, J. R.
Constraints on Helium Enhancement in the Globular Cluster M4 (NGC 6121): The Horizontal Branch Test
2014, The Astrophysical Journal, Volume 782, Issue 2, article id. 85, 8 pp.
(NGC 6121 )
Paper n. 3
Yong, David; Karakas, Amanda I.; Lambert, David L.; Chieffi, Alessandro; Limongi, Marco
Heavy Element Abundances in Giant Stars of the Globular Clusters M4 and M5
2008, The Astrophysical Journal, Volume 689, Issue 2, pp. 1031-1043
(NGC 6121 NGC 5904 )
See all items (6 papers) :: Submit a paper
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