It is the sun, yellow, G Class, with 5 billion years of life left under normal circumstances. General graveyard of heretics and their possessions (no pun intended).
The capital planet of the Imperium, and the most important of them all.
Used to be ruled by gene-cults with a lot of growth vats before the Emperor set off uniting the Solar System. Refusing to be annexed, big Emps sent the XVIth Legion(and co.) upon them, with the gene-cults finally saying "OK, we surrender, call off your wolves." As such, the Luna Wolves were christened.
Home of the Adeptus Mechanicus, and the biggest forge world of all by several degrees of magnitude.
A gas giant Forge World. The Imperial Navy's foremost shipyard and drydock. It only makes ships. It is a hotly contested Imperial political debate as to whether Jupiter is soverign to the Mechanicum or the Imperium. They went totally green though, the hippies.
It once had a Forge Moon, Ganymede, in orbit. It is now Perdita. Do NOT go near Ganymede.
(The fact that there is a bracket here shows how much love GW has given the two planets.)
|The Planets, Systems, Regions and Sectors of the Galaxy|
|Imperial Homeworlds:||Holy Terra - Sacred Mars|
|Primarch Homeworlds:|| Baal - Barbarus - Caliban - Chemos - Chogoris - Colchis |
Cthonia - Deliverance - Fenris - Inwit - Medusa - Nostramo
Nocturne - Nuceria - Olympia - Prospero - Ultramar
|Planets:|| Armageddon - Cadia - Catachan - Ganymede |
Krieg - Kronus - Sacris - Sanctuary 101 - Scelus
Tanith - Tartarus - Vigilus - Vraks - Zayth
|Daemon Worlds:||Plague Planet - Sortiarius|
|Systems and Regions:||Solar System - Jericho Reach - Kaurava System |
Halo Zone - Stygius Sector - Taelus System
|Types of Worlds:|| Agri-World - Craftworld - Daemon World - Death World - Eldar World |
Forge World - Fortress World - Hive World - Tomb World