NGC 5053 was discovered by William Herschel on March 14, 1784 and cataloged as H VI.7.
NGC 5053 is situated just about 1 degree southeast of another, much more prominent globular cluster, M53. As they happen to be at a similar distance, both clusters are spacially quite close together. NGC 5053 is of a much lesser stellar density than its prominent neighbor, and particularly lacks a concentrated bright nucleus.
At a distance of about 53,500 light-years from us, NGC 5053's apparent diameter of 10.5 arc minutes corresponds to a linear extension of about 160 light-years. The cluster shines at a visual brightness of about 9.5 magnitudes, and a photographic magnitude 10.5. Its absolute visual magnitude is only about -6.72, corresponding to an intrinsic luminosity of about 40,000 times that of our sun. It is receding from us at about 44 km/s.
Because of its moderate stellar content, the nature of this cluster as a globular has been doubted in the past, but spectroscopic investigations have now firmly re-established this classification: The stars of NGC 5053 are old and poor in heavy elements. Its horizontal-branch stars are of about mag 16.65, and its brightest stars are at mag 13.8.
It was found that this cluster may perhaps be a former member of the Sagittarius Dwarf Elliptical Galaxy (SagDEG), or Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), the nearby dwarf galaxy discovered in 1994, which is currently in a close and perhaps final encounter before its tidal disruption, with our Milky Way Galaxy.
The image in this page was obtained by Martin Germano with an 8" f/5 Newtonian reflector and ST-8XME self-guided CCD camera and Red filter, exposed 230 minutes.