It goes where? An idea seed for a science fiction campaign.

In the late 21st century, humanity has a tentative foothold within the solar system. There are thousands of humans living off planet scattered throughout the Earth-Moon system and a few transitory outposts on Mars and various near earth asteroids.

On July 6th 2089, observatories and astronomical satellites start tracking a high energy source inbound into the Solar system. Within 5 years it was clear that it was decelerating and would soon enter solar orbit. Over a dozen probes were developed and launched. Finally in 2098, the object entered into a solar orbit between Neptune and Uranus and ceased emitting energy. What remained was a small localized area where gravity was distorted. Barely detectable as stars and planets moved behind the object and then suddenly shifted back to their normal position once they emerged from behind.

The first probes reached the object in May of 2101, what they detected amazed everybody, it was a mechanism of alien manufacture creating an opening to a stable Rosen-Einstein bridge or wormhole several hundred meters in diameter. Upon further investigation the first transit was attempted and when the probe return and its data was analyzed the results were electrifying. It was not just a bridge through space but time as well.

The other end of the wormhole was in the orbit around Earth, Earth of 65 million years ago.