What is the fine-grained topic of the following text: One of the most massive galaxies in the local Universe, it is notable for its large population of globular clusters—about 12,000 compared to the 150–200 orbiting the Milky Way—and its jet of energetic plasma that originates at the core and extends at least 1,500 parsecs (4,900 light-years), traveling at relativistic speed. Only return the topic.
Massive galaxies and their features