A moon
You may be looking for Earth's moon, Luna.
A moon is a generic name for a natural satellite that orbits a planet.
Moons may occur in all varieties concerning their number, form and size. The two moons of Mars are tiny dead planetoids, whereas the Bajoran moon Jeraddo was a planet-sized M-class world, before it was transformed into a wasteland.
More massive moons may also strongly influence their primary planet, as they exert gravitational forces, which can define a planet's orbital period as well as its seasons, like it is the case with Earth's moon, Luna.
Gaila was able to buy his own moon with the income he made from selling weapons. Quark was envious of this for years. In 2373, when Quark began selling weapons with Gaila and Hagath, his cousin told him that after a year of doing so, he would be able to buy his own moon. (DS9: "Civil Defense", "The Way of the Warrior", "Business as Usual")
In an alternate timeline, Quark was able to fulfil his dream and bought his own moon after selling his bar to Morn. (DS9: "The Visitor")