In the movie Star Trek V: The Final Frontier, the Great Barrier is an immense energy field of unknown properties that surrounds the center of the Milky Way Galaxy. Depicted in Star Trek as a a huge thundercloud of gas and dust, the USS Enterprise-A breached the barrier and encountered a planet at the center of the galaxy which was home to Sha Ka Ree - an alien life form whom the followers of the Vulcan Sybok believed to be God.
In real astronomy, the centre of the Galaxy is actually called the Galactic Centre, and is located at a distance of 25,000 light years (7.6 kiloparsecs) away from the Earth. Shrouded beneath a circumnuclear disk of molecular gas and dust, it is home to thousands of stars forming a dense cluster and a supermassive black hole right at the very centre of our Galaxy. Called Sagittarius A*, this supermassive black hole is estimated to have a diameter of about about 93 million miles (the distance between the Sun and Earth) and a mass equal to about 4 million suns.
Although most of the Stars in the Galactic Centre are old red main sequence stars, it is also rich in young, massive stars. Some stars have also been detected in orbit around Sgr A*.