The phrase "stellar remnants" refers to the leftover objects or remains from stars that have finished their life cycle. These can include objects like white dwarfs, neutron stars, or black holes. Full definition
Perhaps the dark clusters contain black holes, or other dark stellar remnants in their cores? (sciencedaily.com)
Unfortunately, the JWST will only be powerful enough to detect such pollutants on Earth - like planets orbiting white dwarf stars, which are incredibly dense stellar remnants of Sun - like mass and Earth - like size. (newatlas.com)
The favourite of the two main explanations was that the positron excess could come from fast - spinning stellar remnants known as pulsars. (newscientist.com)