Einstein-Rosen Bridge

In the early history of the universe, Supermassive blackholes in the centers of galaxies would collide into other supermassive blackholes in the centers of other galaxies. Sometimes they would nearly collide and cause a contusion in space/time around them, creating wormholes and exotic matter in the process.

Huge quantities of exotic matter would be created and force the wormholes to remain for billions of years.

As the universe continually expands and the wormholes aeons old careen throughout the cosmos, some are captured in dark energy field of galaxies.

The milkyway has some 1200 wormholes in its disc. 8 of them are within a 1000 lightyear radius of Sol system. The nearest one is 221 parsecs from the Earth.

The vast distances to these wormholes can be traversed using a Warp-Doughnut type vessel. This type of vessel can achieve speeds of 90 times the speed of light.

A wormhole is roughly spherical shaped, though slightly wider about the equator. The top of the wormhole will usually have the tunnel entrance. There will usually be an accretion disc around the equator and sometimes even planets orbiting the wormhole.

The wormhole itself emmits no light but the exotic matter atmosphere does emmit visible light. A blueish purple indigo color, the intensity of the brightness increases nearer the tunnel.

The tunnel is a vortex that pulls the exotic matter into the throat and holds it open. This tunnel is the part of the wormhole that can be safely traversed.

A wormhole geometry is usually very large, about the size of a star. The tunnel into the throat is very small by comparison, usually only as big in diameter as a minor planet like Earth or Mars.

Inside the wormhole, the gravitational tidal forces are safe enough for space craft and human beings, however, the electromagnetic fluctuation is something that could immediately dematerialize anything that enters. Only a Warp-Doughnut vessel can shield itself from these forces and protect a human crew.