The Solar Church is a multistellar religious faith that boasts some 135 billion members across several hundred worlds.  The extent of Solarian practice goes far beyond the current boundaries of the Republic, out to the former borders of the Empires.  Solarism claims to be the oldest multistellar religion, dating back to pre-empire days or before.  The exact origins of the Solar Church are uncertain, but Church doctrine claims that that it was founded by pilgrims from Reft Sector in 4000 PEC (Pre Empire Calendar).  This area of space is now occupied by the Black Sector, a coincidence that has sparked research and debate alike in the ranks of the Church and it's followers.

Solarism is based on the belief that stars are divine beings, and thus it is considered to be a polytheistic religion.  On many worlds, Solarism is an extension of an existing (and often ancient) practice of sun worship, taking it  to an interstellar scale.  Because of the overlap between existing sun-worshipping practices on worlds, the exact count of Solarian faithful is often in dispute.

The Solarian word Khoamarn (ko-ah-marn) describes an ancient race of beings who shed their physical vestiges to become beings of pure energy, forming the stars and galaxies we see today.

Complementing the Khoamarn in the Solarian doctrine are the Afakhtaa (af-ak-ta), a race of similar beings who fought (and lost) a catacysmic war with the Khoamarn at the dawn of the observable universe.  After losing the great war, the Afakhtaa were banished from the physical universe to the realms beyond.  Many interpret this to mean they occupy jump-space, and further that they are they account for various poorly-understood phenomenon such as anti-matter, black holes, and the Black Sector.

The Solar Church is currently headquartered on Uvaia-6, but this is a recent change since the Eristicon War.  The original headquarters for the church was on Averon, but that world was decimated in a biological war triggered during the Chaos Years.