Hertex

The Mestiko system was a star system proximate to both Federation and Klingon space. It contained seven planets, including one class M world, Mestiko.

By 2265, the Payav, the natives of Mestiko, had explored four of their system's other planets via automated probes, and also established a permanent research base on one of Mestiko's two moons.

In 2265, a rogue pulsar passed through the Mestiko system, causing numerous deaths and significant environmental damage to Mestiko, despite the efforts of Federation scientist Lindsey Cameron and the crew of the USS Enterprise. (TOS eBook: Mere Anarchy: Things Fall Apart)