Stellar Gateways

Also known as a Star Gate, Star Gateway, Keléstial Portal, Godstone or simply portal; Stellar Gateways appear all over the Virgo Supercluster. No one knows who created the gateways but it is known that they harness the energies of Keléstia and can be accessed by dialing stellar constellations to reach a destination. Only one of the portals exists outside of known space and that portal leads to the cosmic Outlands.

Utility

The series of devices scattered across Keléstia create artificial subspace wormholes, allowing for near-instantaneous transportation between two distant points in space.
The Stellar Gateways are, quite simply, "[a] kind of a ring thing, comes with a dialer, you hit the symbols, it spins around and lights come on, it kind of flushes sideways.."
The Stargate creates a stable, artificial wormhole between itself and another, allowing near-instantaneous travel from the dialing gate to the destination gate, but not vice versa. When activated, a Stellar Gateway produces a violent burst of energy known as an unstable vortex or "kawoosh". This is due to the large amount of energy needed to form a stable wormhole, while keeping one open is much less power-intensive. This event will destroy any matter it comes into contact with; however, if the event horizon is blocked to within a few microns, the vortex will be suppressed. Otherwise, the vortex settles into the event horizon, often nicknamed the puddle for its liquid appearance. Travelers enter through the event horizon, which dematerializes them for transport through the wormhole, to be reassembled on the other side. The Stargate will remain open so long as matter or energy continues to pass through it, to a maximum of 38 minutes. Beyond this point, massive amounts of power are needed to sustain a wormhole, which ordinary sources cannot provide.
Travel through a Stellar Gateway is strictly one-way: from the dialing gate to the receiving gate. This is not a limitation of the wormhole, but of the technology; wormholes will transmit anything that enters them, but no solid matter could survive the process. Thus, each gate in the pair takes on a specific role: the dialing gate converts the traveler into its most basic components, sub-atomic particles, and transmits it, while the receiving gate reassembles the transmitted matter back into its original form. Doing the reverse is not only fatal for the traveler, but would just result in the dialing gate deconstructing the object upon arrival, converting it into energy. It is generally unknown what would happen if someone entered the Stellar Gateway via the 'back' rather than the 'front'; few have braved the attempt however and their deaths were "most unpleasant", but further details are unknown.
The Stellar Gateway is an enormous superconductor composed almost entirely of extremely rare strains of what is known as Royal Mithril, and the gateway is capable of harnessing power from virtually any source, though some sources are apparently inferior to others. Its design renders it incredibly durable; direct meteor impacts have failed to destroy a gate, and they have also survived within a crashing vessel unharmed. The Royal Mithril construction of a gateway allows it to hold many times the necessary amount of power for a wormhole to form, but it does have a limit. Surpassing this limit will create an explosion of considerable size, enough to potentially kill all life on a planet the size of Earth.

Usage

Though Stellar Gateways vary in design, they share several common elements. First, all the gateways have a group of glyphs spaced around the inner ring and nine chevrons spaced equally around the outer edge, thirty-nine in all. The glyphs on the gates represent constellations, but not all gateways hold the same set of constellations. These two features are used as a coordinate system for the gate to target and form a connection with another gate; each chevron is locked to a specific glyph, thereby allowing the gate to connect to another. This is known as an address for a gate; gate addresses are described in terms of how many chevrons are needed to dial them, seven at the least and nine at the most.
For a standard seven-chevron address, the first six glyphs represent points in space, forming three-dimensional coordinates. The seventh represents the point of origin, a glyph which is unique to each gate. For Stellar Gateways to access a destination outside of their galaxy, eight chevrons are used; the first six target a destination as normal, while a seventh glyph prior to the point of origin adds a distance calculation to the address, targeting a gate outside the galaxy as opposed to a local one. A nine-chevron address is more of a code than a location, and this allows connection to specific gateways - regardless of their location.
The gateways within a galaxy are linked to each other in a network, usually by means of a Dial Home Device (DHD for short). This network compensates for stellar drift, allowing every gate with a functioning DHD to properly connect to other gates. In the absence of this, the gate will either fail to connect entirely or roughly eject the passengers due to unexpected deviations in the position of the gate.

Glyphs

Glyphs are symbols on Stellar Gateways which chevrons lock onto when a Stellar Gateways is being dialed. The basis for glyphs are star constellations. The gateway has thirty-nine inscribed symbols on the inner ring. When dialing, this inner ring rotates until the dialed symbol is aligned with the seventh chevron, at which point the ring pauses, the seventh chevron moves down and up, and the appropriate chevron in the sequence engages and glows red. The symbols are fixed on the gateway and the entire Gate spins to dial an address. When dialing, the symbols light up to indicate they have been encoded. The glyphs are not based entirely on star constellations since the gate must be able to dial addresses from a moving point of origin in many different galaxies, but rather they are some mathematical or conceptual representation yet to be discovered by the people aboard.

Chevrons

All known Stellar Gateways have nine chevrons used to lock in coordinates. The top chevron 'scans' each co-ordinate and the corresponding chevron lights up. Only seven of these chevrons are normally used. The eighth chevron allows for the establishment of a wormhole to other galaxies. The ninth chevron enables the connection to a specific Stargate.

Dialing Devices

Dial Home Devices (or DHD's) are large, pedestal-shaped computers placed on on almost every planet in the Stargate Network. They establish a wireless link with the nearby Stargate and act as a control device and power source, allowing any intelligent species to dial it without having to rotate the gate manually or develop their own computer interface. Similar to a telephone dial or touch pad (although much larger), the DHD is used to specify which other Stargate to connect to when opening a gate or wormhole to another location. The external symbols on the DHD represent star constellations, surrounding the central activation button. The DHD's are composed of control crystals, used to store memory and information. Despite the apparent simplicity of function, the DHD performs incredibly complex calculations within seconds every time it is dialed to account for stellar drift and other potential problems, assisted by information from its automatic update command.

Complexities of Function

Matter Transmission

Matter transmission is a three-step process: dematerialization, transmission, and reintegration. When an object passes through the event horizon, it is dematerialized and held in a hyperspatial buffer. The event horizon will only dematerialize objects in discrete units (one person, one ship, etc.), so any object which has not fully entered the event horizon can be removed without trouble. The gate does not begin transmitting an object until it has entirely passed through the event horizon. This ensures that only complete objects are transferred. In the case of larger objects such as enclosed ships, the vessel itself counts as a complete object of higher priority than its smaller occupants, preventing transmission until the entire vessel has entered the event horizon. This applies to both the dialing and receiving gates.
Once a object is dematerialized, it is transmitted in the form of energy to the destination gate. Power is supplied by the dialing gate. If the power supply is interrupted, the wormhole can disconnect prematurely, which may prevent the energy from being reassembled into the original object, or simply release the energy into space well short of its destination. If there is any matter in the buffer on either side when the wormhole shuts down, it is stored until the next use, at which point the buffer is erased.
The event horizon on the receiving gate rematerializes the transmitted matter. The matter is first stored in the buffer to make sure the entire object has been retrieved, after which it is reassembled. Furthermore, each time the gate is activated the buffer is wiped clean to receive new information, preventing any possible overlap that could be dangerous to reintegration. If the control crystal of a connected DHD is removed then an event horizon will form without establishing a wormhole, allowing any memory stored in the gateway to be reintegrated.
Several facets of the Stellar Gateway are necessary for it to function as a useful personnel transporter. Matter emerging from a gateway retains any kinetic energy it had while entering; a person running into one gateway will hit the ground running upon emerging from another, and weapons fired into the gate will retain their harmful properties on the other side. The event horizon is able to determine the difference between passive and active contact of nearby matter in order to prevent unwanted transmission. This process keeps things such as air and water, which naturally exert pressure on their surroundings, from passing through the gate while allowing people and anything deliberately sent through the gate to pass freely. In one case, water that mostly submerged a gate (but did not completely cover it) applied constant pressure to the event horizon, keeping the wormhole active for the maximum amount of time. In another instance, the gate is knocked over into a pool of lava, and the lava briefly entered the event horizon before the gate shut down.

Gate Obstruction

A wormhole is prevented from forming if a significant obstruction is present inside the Stellar Gateway's ring. Consequently, it is fairly common for gateways to be semi or permanently sealed by burying them. Another means of controlling travel through a Stellar Gateway is by placing a barrier a minuscule distance (less than three micrometers) from the event horizon, which allows the wormhole to form but prevents the reconstitution of matter upon arrival through the gate. In other words, a connection can be made but any matter trying to exit the gate will not regain its original structure, and hence will be annihilated. Performing this function could be used as an effective defensive precaution, while still allowing radio or magical communication through the open wormhole.
Other interior barriers also suppress the formation of an unstable vortex by not allowing the matter to form. Such barriers, however, are not the only way to prevent the vortex. Some, however, have demonstrated the ability to open a wormhole without the vortex forming, presumably through a more efficient form of energy transmission.

Power Source

Power is always required to establish an outgoing wormhole, and is usually supplied wirelessly by a DHD, but any Stellar Gateway can receive a wormhole whether it has a power supply or not; the dialing gate is the one that supplies power to both. In a few cases, Stellar Gateways have been dialed "manually" when more sophisticated means were not available. This was accomplished by providing sufficient raw power to the gate and then rotating the symbol ring by hand to lock each chevron. Power can be fed directly into the mithril that comprises the gate; power harnessed from lightning strikes has been shown to be sufficient for several seconds of transmission. Gateways also possess the means to harness the energy of nearby (in relative terms) quantum singularities, though it is unknown what methods it uses to accomplish this. The Stellar Gateway that establishes an outgoing wormhole determines how long the wormhole is held open, and can generally close the wormhole "at will". Under some conditions, a gate only needs enough power to connect briefly, then the receiving gate can provide enough power to maintain the connection. The same is true if the outgoing gate loses power while transmitting; if the incoming gate has a DHD, it will take over powering the gate until reintegration is complete.

Durability and Susceptibility

Stellar Gateways are very durable; plenty have been found to be roughly 50 million years old with others being far older still, yet they still function perfectly. Gateways are extremely resistant to damage or destruction. They have survived direct hits from meteors, the gravitational forces of black holes, the heat of a star (this particular gate was protected by a portable force field for a portion of its journey, and was expected to melt eventually), and even bombs sent that destroyed an entire planet left its gateway intact.

Exceptions

Under normal circumstances, a wormhole can only be maintained for slightly more than 38 minutes. This can be circumvented by various means, most commonly through the addition of a massive power supply. A race of energy-rich liquid beings were able to provide enough power for a gate to remain open for several days. One could hold a gate open by transmitting a continuous stream of energy into the event horizon, which would be absorbed by the gate on the other side. The power of such an action could eventually exceeded the gate's capacity, causing it to explode. One could open a gateway indefinitely by firing an immensely powerful laser through it, the gate would draw power from the laser, staying active beyond the limit but one would need a limitless supply of immense power to keep it running as long as necessary.
In addition to massive amounts of power, black holes have been shown to keep a Stellar Gateway open beyond the 38 minute window. Connecting to a gate in the proximity of a black hole, would cause relativity to keep the gate open well beyond the time limit (a mere moment would pass on the other side), while conversely the dial gate would stay open for barely a second when dialed to from that location. Spacial Supergates typically use an artificial singularity as a power source, enabling them to stay open indefinitely if need be, though they are usually left inactive.

Other Uses

Several times, the Stargate network was used for a purpose other than interplanetary travel, although these extra features were almost always discovered by accident, and were not intended in the design of the Stargates. Two such occurrences regard the Stargate's interaction with time, first discovered by SG-1 when they accidentally traveled backward in time to the year 1969, as a result of the matter transmission stream passing through a solar flare. In the year 2010, in an alternate time-line, Samantha Carter intentionally used this phenomenon to send a message back in time. A time loop machine created by the Ancients utilized 14 Stargates to create a bubble enclosed from the rest of the space-time continuum, in which the same day looped continuously.

Discovery

Kèthîra

On Kèthîra, people refer to the Stellar Gateways as Godstones. There are many such gateways on Hârn specifically and like the rest of the world they believe that the Godstones were Earthmaster mechanisms. Though they have the wrong idea of how gateways were created the people of Kèthîra understand that the gateways can be used for near-instantaneous transportation to other places, though they aren't sure were they end up. The people of Kèthîra do wrongly believe that the Stellar Gateway, Godstones, were created around 20,000 years ago by the mysterious Earthmasters.

Toril

There is only one Stellar Gateway on Toril and it rested in Faerûn, forgotten, until a Stellar Rediscovery in 1479 DR. Though books were abound in its hiding place with information on the device, its secrets would not be shared with the world by decree of the Champions of Destiny.