Although it is a solid planet composed mainly of silicon and iron, its inhabitants are entirely airborne; living on floating cities kept aloft by antigrav arrays. It is believed that ancient Estari civilisation was responsible for the toxic lower atmosphere that makes this aerial lifestyle necessary. However, it is now thought that the Estari possess the means to cleanse their homeworld and make it habitable again. The notion is scoffed at by the Estari themselves, who see it as a pointless exercise in denial of the past. Plaidor II, when asked on the matter by a young Homar, remarked "we would not be restoring Estar Prime, we would be making something else".
Estar Prime has no natural satellites.