Trisolaris

Trisolaris is the only planet in the Alpha Centauri system. It is the homeworld of the Trisolarans, the main antagonists of the Three-Body Problem novel trilogy.

Description
Trisolaris is a terrestrial planet, similar to Earth in most respects. However, the Trisolaris system consists of three suns orbiting each other in random and unpredictable ways. This causes Trisolaris to be hurled from star to star during so-called Chaotic Eras, resulting in climate conditions that vary without rhyme or reason. There is no set day or year, and the planet's temperature ranges from cold enough to freeze the air to hot enough to melt the ground. During rare Stable Eras, Trisolaris assumes a steady an comfortable orbit around one of its suns, but this never lasts. Eventually, the instability of Trisolaris' orbit will cause it to crash into one of its suns, destroying it and the Trisolaran race.

Because of this, Trisolaris is incredibly hostile to life, and the Trisolarans are desperate to leave. They set their sights on Earth, a planet existing in a perpetual Stable Era.

History
Trisolaris was originally one of twelve planets in the Alpha Centauri system, but the eleven other worlds all fell into the system's suns. It was the only one of these worlds known to have evolved life.

Trisolaris' natives evolved hundreds of separate civilizations, but all were destroyed by Chaotic Eras. The worst of these disasters was a close passage by all three suns, literally tearing the planet in two and forming a massive moon around the main planet. Civilization did not re-emerge for ninety million years.

Eventually, the Trisolarans realized that their planet's problems could not be solved and sought to abandon it. Discovering Earth, they directed a massive colonization fleet to the Solar System, which would take hundreds of years to arrive. Not long after the fleet left, Trisolaran leaders constructed "sophons," sentient protons that could travel to Earth at light speed and transmit data back to Trisolaris in real time.

The Trisolaran fleet sent a deadly "droplet" probe as a vanguard, which singlehandedly wiped out Earth's entire space navy in the so-called Doomsday Battle. However, invasion was halted by the threat of the dark forest broadcast, a signal that would call down extremely powerful and hostile aliens on both Earth and Trisolaris. The threat of this broadcast diverted the first fleet, but a second, much faster fleet was constructed and sent from Trisolaris. A Trisolaran surprise attack briefly conquered Earth in preparation for the second fleet, but this triggered the dark forest broadcast.

The use of the dark forest broadcast ended the conflict between Trisolaris and Earth by dooming both worlds. Trisolaris was destroyed by a relativistic projectile which gouged open one of its suns, engulfing the planet in the star's contents. Only the Trisolarans aboard the invasion fleets survived.