What?
I think you might be referring to pictures of nearby galaxies which often show a bright central core surrounded by the rest if the stars. Spiral galaxies have dense nuclei containing billions of stars all crowded together but still light years apart. But from a distance, the effect is to see a very bright, luminous spot in the center of the galaxy. Around the turn of the century, nearby galaxies were called 'island universes' but today we reserve the term 'universe' to describe the entire system of galaxies we can observe out to billions of light years.