SpaceX launched three rich businessmen and their astronaut escort to the International Space Station on Friday for more than a week's stay, as NASA joins Russia in hosting guests at the world's most expensive tourist destination.

It's SpaceX's first private charter flight to the orbiting lab after two years of carrying astronauts there for NASA.

Arriving at the space station Saturday are an American, a Canadian and an Israeli who run investment, real estate and other companies. They're paying $55 million apiece for the rocket ride and accommodations, all meals included.

Russia has been hosting tourists at the space station—and before that the Mir station—for decades.

The search for extraterrestrial life and exploration of "another Earth" is an eternal theme for humans and inspires generations of planetary scientists. It not only improves our understanding of the formation and evolution of planets during the formation of a star system but also helps scientists to investigate the possible conditions and criteria of the existence of life. In the past 30 years, scientists have discovered more than 4,000 exoplanets, but exploration still has a long way to go.

Due to the far distance, searching for exoplanets requires high sensitivity and high resolution.