Brasilios

Brasilios is a fictional planet featured in the science fiction novel "Project Hail Mary" by Andy Weir. It is the home world of the alien species known as the Eridians. The planet is located in the Tau Ceti system and is characterized by its atmosphere and surface conditions, which are suitable for Eridian life but hostile to humans.

The Eridians, also known as the Astrophagi, are a sentient species that evolved on Brasilios. They are described as having a unique physiology adapted to their home planet's environment. Brasilios itself is depicted as a world with significant atmospheric pressure and a composition that differs greatly from Earth's. This environmental adaptation is crucial to understanding the Eridians' biology and their interactions with humans in the narrative.

The planet plays a significant role in the plot of "Project Hail Mary" as it is the origin of the Astrophage, a microorganism that consumes solar energy and threatens Earth's sun. The Eridians, through their own experiences with the Astrophage on Brasilios, have developed methods to combat it. The human protagonist, Ryland Grace, travels to the Tau Ceti system to seek a solution to the Astrophage crisis, leading to his encounter with the Eridians and their homeworld. The descriptions of Brasilios are integral to establishing the alien nature of the Eridians and the challenges faced by humanity.