Multiple realities(covers information from several alternate timelines)
Heaven was a mythological paradise in many cultures. The term could also be synonymous with the sky.
Since ancient times, Bajorans have believed that the pagh of the faithful will "walk" with the Prophets (who reside in the Celestial Temple) after death. (DS9: "Emissary", et al.)
In the 17th century, John Milton of Earth wrote in his poem Paradise Lost that "It is better to rule in Hell than serve in Heaven." (TOS: "Space Seed")
In 1996, when Porter observed Lieutenant Tuvok using a phaser, he believed it to be a laser and commented "God in Heaven help us," but The Doctor replied that divine intervention was unlikely. (VOY: "Future's End, Part II")
In the 22nd century, Kai Taluno of Bajor claimed his ship was "almost swallowed by the heavens" near the Denorios belt. In fact, he had most likely witnessed the opening of the Bajoran wormhole. (DS9: "Emissary")
In 2152, Captain Jonathan Archer noted that Porthos, ill from a pathogen, had "one paw in beagle heaven" while he expressed frustration about the Kreetassans and T'Pol to Doctor Phlox. (ENT: "A Night in Sickbay")
The Children of the Son believed that the stars were light from heaven coming through. They also believed the Son resided there. (TOS: "Bread and Circuses")
In 2366, Geordi La Forge stated that he hoped the non-corporeal Koinonians invading the ship's systems wouldn't "blow us to Kingdom Come while (they're) figuring out how to blow us to Kingdom Come." (TNG: "The Bonding")
Heaven was mentioned in the Albert King song "Everybody Wants to Go to Heaven", which remarked "Everybody wants to go to heaven, but nobody wants to die". (Star Trek Into Darkness)
Heaven was referenced in the final draft and the revised final draft of the script for TOS: "The Enemy Within", which described space as "
heaven for some... hell for others...."