NGC 6553

NGC 6553 is a globular cluster in the constellation Sagittarius. NGC 6553 has an apparent magnitude of about 8th magnitude with an apparent diameter of 8.2 arcminutes.[2] Its Shapley–Sawyer Concentration Class is XI,[2] meaning the star concentration is very loose even at the center; it has stars of magnitude 20 and dimmer. It is located just over a degree southeast of Messier 8, the Lagoon Nebula.

NGC 6553
The globular cluster NGC 6553 imaged by Hubble
Observation data (J2000 epoch)
ClassV
ConstellationSagittarius
Right ascension18h 09m 15.68s[1]
Declination−25° 54′ 27.9″[1]
Distance19.6 kly
(6.01 kpc)[1]
Apparent magnitude (V)8.06[2]
Physical characteristics
Radius4.1' x 4.1'[2]
Metallicity = -0.18[3] dex
Other designationsGCl 88, C 1806-259[1]

Unlike common globular clusters, NGC 6553 is relatively metal-rich, and there is evidence of at least two periods of star formation.[4] Due to a complex star-forming record, the stars in the cluster are differing in composition, most notably in concentrations of sodium and aluminium.[5]

NGC 6553 is very similar in composition to NGC 6528, suggesting an origin in a similar environment.[6]

References
  1. "NGC 6553". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 January 2017.
  2. "NGC 6553". Retrieved 8 January 2016.
  3. "A Galactic Globular Clusters Database: NGC 6553". Retrieved 8 January 2017.
  4. Two Groups of Red Giants with Distinct Chemical Abundances in the Bulge Globular Cluster NGC 6553 Through the Eyes of APOGEE, 2016, arXiv:1610.06763
  5. The vertical Na-O relation in the bulge globular cluster NGC 6553, 2019, arXiv:1912.03742
  6. Chemical analysis of NGC 6528: one of the most metal-rich bulge globular clusters, 2018, arXiv:1809.04164


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