The Universe is the home of the Humans, which has rather typical particle content and large scale structures. The worlds of the Universe include most importantly the worlds of the Solar System, and other star system further away.
The Sun - The star that supplies the Humans with all of their energy. It is one of the lighter stars of the Universe.
Mercury - The closest planet to the Sun, being a source of many raw materials for the Humans. It has no atmosphere and is in a spin-orbit resonance with the Sun.
Venus - An unreasonably hot planet for the Humans, which opt to instead build settlements up in the clouds of the extremely thick atmosphere. Filled with clouds of carbon dioxide that trap the heat, along with sulfuric acid clouds that terrorize the floating settlements.
Earth - The origin planet of the Humans. Oceans of water support the ecosystem that has produced the humans. Earth has a major satellite that is a rocky atmosphereless world, the Moon. Many megastructures have started their construction on the Earth, or in orbit, or on the Moon.
Mars - A reddish planet with a thin atmosphere, once a seemingly unachievable target of the Humans. It now has various settlements and cities.
Jupiter - The largest planet in the Solar System, a gas giant with four major moons that have had many artifacts of the Gone. Jupiter and its moons are places with huge cities and the main gateways to the other universes of the Multiverse.
Saturn - A gas giant planet known by the Humans for its rings and several moons. Unlike its neighbor Jupiter, Saturn has turned up relatively dry for Gone artifacts. Saturn's moon, Titan, was one of the first places that Humans have discovered life outside the Earth, however its discovery was quickly overshadowed by the Multiverse.
Uranus - A pale blue planet with major artifacts like Jupiter. Uranus also has large cities on its moons, and various gateways opened by humans.
Neptune - It's slightly bluer than Uranus.