Pernaia Prime was the uninhabited prime planet in the Pernaia system. It had a methane-based atmosphere, and did not support life. It had a single, frozen moon, and was approximately one hundred light years from the Sol system.
In 2152, the Vulcan Security Ministry tracked down the fugitive Menos to the Pernaia system. They sent T'Pol, who brought Captain Archer and Ensign Mayweather, to track him down and capture him. Commander Tucker believed they were going to Pernaia Prime until he realized that planet had a methane atmosphere. He then deduced that his crewmates were heading to another location in the system; they were in fact going to Pernaia Prime's moon. (ENT: "The Seventh")
The Star Trek Encyclopedia, 4th ed., vol. 2, p. 134 classified Pernaia Prime as a gas giant.