Messier 53 (also known as M53 or NGC 5024) is a globular cluster in the Coma Berenices constellation. It was discovered by Johann Elert Bode in 1775. M53 is one of the more outlying globular clusters, being about 60,000 light-years (18.4 kpc) light-years away from the Galactic Center, and almost the same distance (about 58,000 light-years (17.9 kpc)) from the Solar System. The cluster has a core radius (rc) of 2.18 pc or about 7 light-years.

M 53 is considered a metal-poor cluster and at one time was thought to be the most metal-poor cluster in the Milky Way. Abundance measurements of cluster members on the red giant branch show that most are first-generation stars. That is, they did not form from gas recycled from previous generations of stars. This differs from the majority of globular clusters that are more dominated by second generation stars. The second generation stars in NGC 5024 tend to be more concentrated in the core region. Overall, the stellar composition of cluster members is similar to members of the Milky Way halo.

A tidal bridge-like structure (not visible in the image) appears to connect M53 with the close, very diffuse cluster NGC 5053, as well as an envelope surrounding both clusters. These may indicate a dynamic tidal interaction has occurred between the two clusters; a possibly unique occurrence within the Milky Way since there are no known binary clusters within the galaxy. In addition, M53 is a candidate member of the Sagittarius dwarf galaxy tidal stream. 

Only 1° (or 2 kpc) away is NGC 5053, a globular cluster with a sparser nucleus of stars. Its total luminosity is the equivalent of about 16,000 suns, one of the lowest luminosities of any globular cluster. It was discovered by William Herschel in 1784.This is a metal-poor cluster, meaning the stars have a low abundance of elements other than hydrogen and helium. As recently as 1995, it was considered the most metal-poor globular cluster in the Milky Way.

Globular stellar clusters M 53 and NGC 5053, 4 & 5 March 2025, Kempen, 

William Optics APO 110 mm, f/7, ASI1600mm pro, LRGB, L(2640 s), R(1800 s), G(1680 s), B(1800 s). 

Image processing with PixInsight V1.9