In order of closest to farthest from the sun:
Known as Karline by its denizens, it is a scarcely populated Death World, shrouded in darkness. It is used mainly as a training world for the Hammer Guard, to test aspirants in preparation of becoming neophytes. It is filled with nocturnal creatures and plants, most of which are carnivorous. The few humans that live there live towards the north, where the light shines for 5 hours a day instead of 4.
The capital of the sub-sector, the planet Solaritus II is often called Solaritus Solar, and is classified as a Civilized World and is highly populated, with 2 Hives and many smaller cities dotting the planet. It has a lush green environment and is constantly raining, cuasing the capital hive, Hive Sealtus, to have raised almost a kilometer above the Island it rests upon so that the lower levels do not flood. It is ruled by Governor Jarconic Vendi, a truly odd Governor in the fact that he cares about the civilians of the planet he rules over, and is constantly trying to make life better for them. In doing this, however, he has almost completely turned his back on the rest of the sub-sector, only checking in to make sure they are still functioning properly. After the Siege of Solaritus, when the system was attacked by a massive Chaos Warband, the regiments coming from Solaritus are trained in Siege Warfare, most notable the 2nd Solaritus Siege regiment.
Once the proud jewel of the Solaritus sub-sector, the former homeworld of the Hammer Guard sits, lifeless. Where great forests and lakes were there is now only ash and ruins. The planet known as Gabarlos to the Hammer Guard and the other residents of the sub-sector, was once a Feudal world, ruled over directly by the Hammer Guard. It boasted beautiful lakes and trees the size of skycrapers, but it's greatest feature was the Anvil, the Fortress Monastery of the Hammer Guard, built into Mount Carion. All that was burned away when the Ordo Xenos called exterminatus on the planet, destroying the Ork infestation as well as all over life on the planet, including those civilians who had not escaped along with the Hammer Guard's 7th company. Now it is a barren world, devoid of all life, a constant remind of just how real the threats to the Imperium are.
A massive Hive World, Solaritus IV's citizens lead lives of constant misery, with only a chosen few earning enough favor from Govenor Karn Sulliveni to live in the Upper Districts. The land outside the hives is a toxic wasteland, and the world is all but bare of plant life, save for the few agricultural factories or the gardens of the upper hive. It is from the gangs of the lower hive the Adeptus Astartes draw their recruits, knowing they are some of the toughest fighters in the sector. There are many that cry a different name for the planet, to spite the governor, Pompeil.
A Feral World with a predominantly Taiga biome. Solaritus V's 2 Billion natives are ruled over by the tyrannical governor Sterfal DeVrom, who rules over the planet with an iron fist. The few dissenters and patriots refer to it as Devax Victri. It is the primary recruiting world for the Hammer Guard in the sub-sector.