Questar M-17 was a dead star with negative star mass located on the edge of explored space. A spectral analysis of the star revealed imploded matter.
On stardate 5221.3, the USS Enterprise investigated the dead star while star charting. After becoming trapped in the star's hypergravity, and achieving orbit, the crew discovered an ancient unknown vessel in orbit of the star remnant.
A magnetic organism living inside the ancient ship returned to the Enterprise along with the away team and subsequently took control of that vessel. The Enterprise escaped, trapping the organism in Questar M-17's magnetic field. (TAS: "Beyond the Farthest Star")
Questar M-17
Questar M-17 inhabited by an unidentified magnetic organism.
According to Star Trek Maps (Chart A), Questar M17 was located near the disputed border between the United Federation of Planets and the Tholian Assembly on the Federation side.
According to Star Trek: Star Charts (pg. 13), "Quasar M17" was located in the Beta Quadrant, at the fringe of the Milky Way Galaxy, near the galactic barrier.