Star Trek: What Is The Galactic Barrier?

With all of the roaming around the galaxy that takes place in "Star Trek," it's easy to forget that the universe is immeasurably vast and extends far beyond the Milky Way galaxy and even our Local Group, the galactic neighborhood that includes the Andromeda Galaxy and dozens of dwarf galaxies. But checking out our space neighbors isn't as simple as cruising at warp 9 until you or your generational ship descendants get there. This is thanks to the galactic barrier, a trippy, mauve-colored energy field wrapped around the Milky Way. Although not completely impenetrable depending on who you're asking, the barrier creates serious problems for most who encounter it.

The barrier shows up early in "Star Trek: The Original Series," first appearing in the second "Star Trek" pilot episode, "Where No Man Has Gone Before," where it was described in the script as appearing similar to an aurora borealis. The Enterprise crew first learns of it while decoding the memory banks of the S.S. Valiant's black box, which reveals the doomed ship catastrophically collided with the galaxy's edge after being swept toward it by a "magnetic space storm" in 2065.

Throughout Starfleet's many encounters with the boundary, the galactic barrier displays many strange properties. While Enterprise deflectors seem to detect it, their sensors do not. And according to Spock (Leonard Nimoy), the barrier registers negative for radiation, density, and energy. Despite this, the field can heat a ship's hulls to more than 2000 degrees, causing extensive damage to systems and warp drives and sending energy shocks through the ship ("By Any Other Name"; "Where No Man Has Gone Before"). When two members of the crew previously found to have high ESP are struck by these charges, their mental powers become amplified, transforming them into godlike beings.

As rough as the galactic barrier is on humanoid forms and most vessels, several members of the non-humanoid Kelvan Empire (not to be confused with "Star Trek's" Kelvin timeline) once survived a disastrous attempt to cross it, as Kelvan leader Rojan (Warren Stevens) recalls in the "TOS" episode "By Any Other Name."

Aware that increasing radiation would eventually make life in the Andromeda galaxy uninhabitable, the Kelvans sent generational ships out in many directions to find another world to take over. Rojan's crew was eventually able to break through the galactic barrier into the Milky Way, but the damage to their ship was too great, and the Kelvans narrowly survived by escape pod. To make matters worse, no known form of transmission can make it through the barrier, which leaves them no way to connect with their home world short of hijacking a Federation ship and modifying it enough to limp through the barrier. When the Enterprise crosses the barrier again in "Is There No Truth in Beauty?," getting propelled into a spacetime void at speeds exceeding warp 9.5, they manage to escape the deleterious consequences they experienced in their last two encounters with the boundary.

Nearly a millennium later, the USS Discovery runs into trouble at the galactic barrier while investigating one of the biggest unanswered questions in "Star Trek: Discovery." In pursuit of answers surrounding the mysterious Dark Matter Anomaly (DMA) and its origins in "Stormy Weather," the crew learns the DMA originated outside of the boundary. The Discovery later crosses the galactic barrier intentionally in order to make contact with the DMA's creators, traveling via stable space bubbles to get there and using the DMA wormhole to return home with help from Species 10-C ("The Galactic Barrier"; "Coming Home").