The K'ntarians are an alien civilization. Their exact location in the galaxy has not been mentioned and it is unclear how much is know about them within the fictional tapestry of Astro City stories. One item is certain, Starwoman, a founding member of Honor Guard, is a K'ntarian.
They seem to have significant political clout and power among the various species and cultures that inhabit the nearby region of the galaxy. Following the attempted invasion of earth by the Enelsians, the K'ntarians, working within guidelines established by the Galactic Council played a major role in brokering a proper and impressive punishment.
Starwoman and the K'ntarians have also left a powerful device on earth, called the contact matrix. It's main purpose is a communication conduit, to be used by Honor Guard or other high-level authorities on Earth.