Astronomical and Imaging Data

Useful Informations

The globular cluster ESO 452-SC11 is one of the faintest and least studied stellar clusters belonging to the Milky Way Galaxy. ESO 452-SC11 is the object’s formal designation from the European Southern Observatory (ESO) survey, where “452” refers to the survey plate number and “SC11” indicates it is the 11th star cluster identified on that plate. The 1636-283 name is an abbreviated form of the cluster’s celestial coordinates, specifically its Right Ascension (RA) and Declination (Dec), which pinpoint its position on the celestial sphere. The first part, 1636, represents the approximate Right Ascension (RA) in hours and minutes (16 hours, 36 minutes). The second part, -283, represents the approximate Declination (Dec) in degrees and arcminutes (-28 degrees, 3 arcminutes).

Location and Kinematics

The cluster is located near the boundary of the Galactic bulge or in the inner halo of the Milky Way. Its coordinates place it in the constellation Scorpius. It is situated approximately 27000 light years from the Sun and about 7000 light years from the Galactic Center. Observations have determined a radial velocity of roughly 17 kilometers per second, indicating its movement relative to the solar system.

Physical Properties

ESO 452-SC11 is considered a low mass globular cluster. Its total estimated mass is around 6800 solar masses. Its small angular size on the sky corresponds to a physical diameter of only a few parsecs. It has a relatively faint apparent visual magnitude of approximately 12th mag.

Stellar Composition

The cluster is notable for being relatively metal rich for a globular cluster, with a measured metallicity of approximately minus 081 (or 081 dex below the Sun’s metal abundance). This composition suggests a later formation epoch compared to the most metal poor globular clusters.

Significance of Multiple Populations

A key scientific finding regarding ESO 452-SC11 is that it shows indications of multiple stellar populations, which is evident from star to star variations in light element abundances such as carbon and nitrogen. This is an unusual characteristic for a cluster of such low mass, as this phenomenon is typically only seen in much more massive globular clusters. This observation makes ESO 452-SC11 an important object as it sets a tentative lower mass limit for the occurrence of the multiple stellar population phenomenon.

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