Nuclear star cluster

A nuclear star cluster (NSC) or compact stellar nucleus (sometimes called young stellar nucleus) is a star cluster with high density and high luminosity near the center of mass of most galaxies.

[1] NSCs are the central massive objects of fainter, low-mass galaxies where supermassive black holes (SMBHs) are not present or are of negligible mass.

Some galaxies, including the Milky Way, are known to contain both a NSC and a SMBH of comparable mass.

With apparent magnitudes between -14 and -10 mag in the infrared, they are on average 40 times brighter than globular clusters, although their effective radii are not larger than 2 to 5 parsecs.

[3] The majority of nuclear star clusters contain a mix of old (at least one billion years old) and young stellar populations and show signs of star formation within the last 100 million years.