Trisolaris

Trisolaris is a planet in the Alpha Centauri System. Its chaotic orbit around the system's three suns renders the planet extremely hostile even to its native life, forcing the Trisolarans to seek a new home on Earth.

Orbit
Trisolaris is defined by its highly unusual orbit. It orbits all three of its suns and is continually tossed between them, resulting in days and years of random and unpredictable length. The rare occasions when the planet enters a stable orbit around a single star are called Stable Eras, and the intervening periods are called Chaotic Eras. Chaotic Eras are highly disruptive to Trisolaran societies and sometimes destroy them outright.

Climate
Trisolaris seemingly has an Earth-like climate during Stable Eras, and it is known to have an Earth-like atmosphere consisting mainly of nitrogen and oxygen. During Chaotic Eras, however, its climate changes dramatically at random intervals. Depending on Trisolaris' distance from the closest sun, it can swing rapidly between arctic cold and searing heat. Trisolaris can reach temperatures close to absolute zero at its furthest from the three suns, and should it come close to all three, its temperatures can rise high enough to melt rock.

Terrain
Little is seen of Trisolaris' surface. However, it appears to consist largely of plains, which are covered in plant life that hibernates during the planet's Chaotic Eras. During Chaotic Eras, the plains are either frozen over with permafrost or covered in boiling mud. Trisolaris also has oceans and seas, although these often boil or freeze during Chaotic Eras.

History
Trisolaris was originally one of twelve planets in its solar system. However, over time the other planets' chaotic orbits decayed, sending them crashing into the suns and destroying them. Eventually, Trisolaris was the only planet that remained.

Numerous civilizations arose and fell on Trisolaris, one after the other. These civilizations attempted to determine the reasons for their homeworld's Chaotic Eras, but the Chaotic Eras destroyed almost all of them before they were able to. However, the Trisolarans never went entirely extinct due to their hibernation ability.

Around 90 million years ago, Trisolaris passed close to all three of its suns. The tidal forces of this passage literally ripped the planet in two, tearing off around a quarter of its mass. This fragment eventually became a moon of Trisolaris. All life on the moon, and most of that on Trisolaris itself, was wiped out. Civilization would take 90 million years to re-emerge.