Not much is known about the planet, aside from the fact that it is situated somewhere in the galaxy, and that it was destroyed by Galaxia. At the time of the destruction, the injured Kakyuu fled, eventually landing on Earth, and in the care of Chibi-Chibi. To find her, the Starlights disguised themselves as men.
Exactly what the conditions of Kakyuu were before the destruction is unknown in both the anime and manga, though both present some varying information about what it was like. For example, Kakyuu is known to have been the princess of the Red Ceres kingdom on Kinmoku in the manga, but it is unknown as to whether this was a worldwide kingdom (similar to Elysion or Silver Millennium) or one kingdom out of several. The anime, on the other hand, seems to infer that Kakyuu was the princess of the entire planet. The anime also shows Kinmoku as being flanked by three tiny satellites - each representing the Starlights' home planet, or at least the moons of Kinmoku that they represent.
The word 'Kinmoku', in romanji, is a pun of another Japanese word, Kinmokusei, a kanji word. The kanji word refers to a specific type of red-orange olive, the osthmanthus (fragrans) aurantiacus.