Galactic Barrier
- Barrier of negative energy surrounding the Milky Way galaxy, source unknown
- No known types of subspace transmissions able to penetrate the barrier (TOS: "By Any Other Name")
- Invisible at distance
- Only visible when in proximity, manifesting the appearance of a wide purple/pink band of energy ahead of travel (TOS: "Where No Man Has Gone Before")
- Early sensors unable to detect barrier
- First detection by Federation only identified by discontinuity in interstellar medium (TOS Novel: The Captain's Oath)
- Long-range probes launched by Delta Vega Mining Consortium in preparation for establishment of Delta Vega (TOS Novel: The Captain's Oath)
- Starfleet sensors of 2265 unable to, but later upgrades functioned properly (TOS: "Where No Man Has Gone Before", "By Any Other Name")
- First detection by Federation only identified by discontinuity in interstellar medium (TOS Novel: The Captain's Oath)
- Incredibly dangerous to pass through
- Requires specially designed shielding and engine technologies to be able to leave or enter the Barrier (TOS: "Where No Man Has Gone Before", "By Any Other Name")
- Proximity results in extreme interaction with individuals of high esper or telepathic potential (TOS: "Where No Man Has Gone Before")
- Individuals with low esper rating show no effect (TOS: "Where No Man Has Gone Before", "By Any Other Name", "Is There in Truth no Beauty?")
- Individuals with moderately high esper rating die as a result of psionic overload (TOS: "Where No Man Has Gone Before")
- Individuals with extremely high esper rating gain rapidly accelerating telekinetic and telepathic abilities (TOS: "Where No Man Has Gone Before")