Grayson was located in the Yeltsin's Star System, 31 light years to the north east of the Manticore System, over five hundred light years away from Earth, and two days travel west of the Endicott System. (HH2)
It was the only habitable planet in its system, with a population of around four and a half billion humans around 1905 PD. (HH2) It orbited its star at a distance of about 13.5 light minutes. (Companion)
The planet was not as large as Earth and had a blue-green color to it because of the massive amounts of chlorophyll. There were few deserts. Grayson had a high concentration of heavy metals, such as arsenic and cadmium. None of the native fauna and flora were edible to humans, and the water was too acidic to drink. Most of the metals were worth attracting much interstellar trade.
Due to heavy metal poisoning and the lack of modern medical technology until the alliance with Manticore, the inhabitants of Grayson experienced stunted physical growth and shortened lifespans. Visitors from other worlds carried a filtration mask because of the high concentration of heavy metals in the atmospheric dust. (HH2) The need to minimise metal intake in the Grayson diet created a strong pressure for the development of orbital farms until the introduction of crystoplast domes for farms by Grayson Sky Domes, Ltd. (HH5)
The planet was settled by the Church of Humanity Unchained, led by the Reverend Austin Grayson, at the end of the 10th Century PD. (HH2) It was originally called "Zion", but soon after the Reverend's death its inhabitants began to refer to it as "Grayson's World", which was eventually shortened to just "Grayson".
- See History of the Protectorate of Grayson for more details.
- In the early 20th Century PD.