Star Gate
Ringworlds have the ability to create artificial wormholes to other solar systems with limitless range. Each ringworld arc contains a set of four enormous particle accelerators parallel to each other. When activated, the ringworld particle accelerators harness the power of the sun to open multi dimensional portals, enabling travel across the universe instantly.
Creating these artificial wormholes requires a preon particle, harvested from the target star. This means it isn't possible to create a connection to an unexplored system.
The Relic tutorial story also explains their functionality and some of the lore.
Control Center
All ringworlds have a control center. It is always located on arc 1 at 0°E 0°N.
The control center looks like a square platform with an obelisk in each corner, in the middle is a tiny hologram of the ringworld.
At the control center it is possible activate the ringworld's star gate function, which will power up the ringworld and create an artificial wormhole at its host sun.
The sun appears at the hologram's center, lighting the ringworld. The lighting shows the current night and day areas of the ringworld. In addition, a blinking spot appears on the ringworld as a "you are here" marker. Other light sources, such as your EV suit light and vehicle lights, may interfere with the hologram so it is best to extinguish them.
Wormhole
The star gate is activated simply by dropping the preon particle on the control center's platform.
The control center will take one preon particle from the platform every cycle. A cycle starts when the four obelisks have a flashing red light on top. This light also shows when the star gate is ready to be activated, and the shadow panels are in position for an activation. You cannot visually look up and see when the shadow panels are in position to open a stargate, the obelisk lights must be used.
Note: The obelisk lights are only visible when you are standing on the flat part of the central platform.
When the cycle ends, the artificial wormhole dies. This means that activating the star gate close to the end of a cycle will cause a very short lived wormhole.
The artificial wormhole will appear at 0°E 90°N of the ringworld's star and the exit will appear at 0°E 90°S of the destination solar system's primary star. The exit wormhole always appears at the primary star, even if the preon particle was harvested from a companion star.
The originating wormhole created is positive and the destination wormhole is a negative wormhole, in other words it is a two-way wormhole just like naturally occurring wormholes. This means that it is possible for spacecraft at the destination to travel through the wormhole to the ringworld system and vice versa.
While the stargate is active, and you are within the relevant solar systems, a new type of order will appear near the top of the order list (New Mission) on the Spacecraft (F9) window. This will say "Travel Via Stargate", and the option will be the destination system. This new order appears above "Travel Via Wormholes". This order lets the AI crew automatically use the new artificial wormhole.
While the star gate is active, the ringworld's particle accelerators will be firing particle beams at the ringworld's star. The light output from the origin and destination stars is reduced by half while the star gate is open, giving them a darker appearance. Farms, orchards and solar power plant production may be affected. Semi-habitable outer worlds could drop below the light level needed for the locals to work without electrical power. These conditions are temporary, passing when the star gate closes.
Lore
Legends describe an ancient Empire that spanned the Universe. Their expansive reign was made possible by building a vast network of interconnecting star gates. To accomplish this feat, they developed technology to build ringworlds using the crushed remains of planets that once orbited the ringworld's sun. As the Empire spread among the galaxies, they built their ringworlds, a lasting testament to the former glory of the Empire.
A steady supply of preon particles at each end of the star gate connections maintained valuable arteries of travel that heralded a golden age of civilization in the Universe. All empires fade in time, rotting from within. Greed led to war. With their cities battered and cratered, preon harvesters stopped returning from their missions. Connections were lost; the network broke down and disintegrated. Daunted by the star travel needed to reconstruct the network, the empire withered, faded into obscurity. This was the beginning of the dark ages of their downfall.