A map of the Milky Way Galaxy
M80 was a globular cluster in the Delta Quadrant. It was located over forty thousand light years from the galactic core.
The location of M80 was shown on Federation star charts in astrometrics aboard the USS Voyager during the later years of its seven-year journey in the Delta Quadrant. (VOY: "Inside Man", et al., display graphic)
In an alternate timeline, the star chart depicting Voyager's flight path home was also displayed in Captain Harry Kim's ready room aboard the USS Rhode Island in 2404. (VOY: "Endgame")
The graphic is shown in legible detail in Geoffrey Mandel's Star Trek: Star Charts (pp. 76-77).
According to the Star Trek: Star Charts (p. 82) and the Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), M80 was a quasar.