Nolia Prime, a world distantly orbiting an orange dwarf in the Sophic League Outer Regions, is illuminated by three artisuns
Artisuns are orbiting sources of illumination that can provide light and heat to a planet or megastructure. These devices are generally powered by fusion or by matter conversion, although a few examples are powered by fission or power extracted from a magnetic field. One of the most common uses for artisuns is to provide illumination to the dark side of a Vesperian (tidally-locked) world.
Artisuns are also relatively commonplace around worlds and megastructures that are located far from any convenient star, and are often found in Deeper Covenant polities. Because of the light and waste heat they emit, these devices are less common among Hiders who do not wish to be observed easily. A small fraction of Hider habitats have their interiors illuminated by a large Hotpoint which acts like an artisun. However this option produces a considerable amount of waste heat, which could be detected by outside observers (something most Hiders wish to avoid).
In most cases an Artisun does not emit light isotropically (in all directions), but instead includes a reflecting system that directs the emitted light in a particular direction, like a spotlight. Some artisuns illuminate rotating rings and cylinders like a luminaire and are shaped accordingly, although in many cases luminaires are powered by collected stellar luminosity.
Both Class 1 and Class 3 sunlines are similar in concept to an artisun, since they both use the atmosphere of a gas giant for fuel in order to produce light and power. Artisuns, however, are generally much more compact devices, and need to be supplied with fuel from an outside source on a regular basis.
An increasing number of artificial suns of various designs are found in systems which are being, or have been converted into Matrioshka Hypernodes. In such a system, the local star is disassembled by star-lifting, and the resulting material is burned in a controlled way to provide power for a range of uses.
On a smaller scale, some Matrioshka Micronodes perform the same function by disassembling a gas giant world. In both cases, one popular option is to construct an artificial planet with its own gravity, and illuminate this with artisuns.