What is the name of the planet in Stanislaw Lem's 'Solaris'?

The planet in Stanisław Lem’s novel Solaris is named Solaris. The 1961 novel follows psychologist Kris Kelvin, who arrives at a research station orbiting the distant world to investigate strange events among its scientists.

Solaris is unlike a conventional inhabited planet. Much of its surface is covered by a vast, living ocean that researchers suspect is a single extraterrestrial intelligence. The ocean produces temporary formations and seemingly human replicas drawn from the memories of people at the station, making the scientists confront grief, guilt, and the limits of human understanding.

Readers sometimes confuse Solaris with the title of the novel, but both refer to the same fictional world. It is also easy to mistake the book for a conventional first-contact adventure. Lem’s central question is more unsettling: can humans communicate with an intelligence so fundamentally unlike themselves that its actions may not even be recognizable as communication? The novel inspired major film adaptations by Andrei Tarkovsky in 1972 and Steven Soderbergh in 2002.