Kepler-6b is the only planet that has been discovered in the orbit of Kepler-6.

It is still the only planet we've ever been to.

Kepler-8b is the only planet that has been discovered in the orbit of Kepler-8.

At present, the Earth is the only planet we have detailed information about.

Yet it had been the only planet available for the Matriarchate.

I'm not a member of anything, but wasn't Earth once the only planet?

It is currently the only planet known to exist in this star system.

The only planets that could spring to new life thanks to advanced technology must be truly dead.

Kepler-7b is the only planet that has been discovered in Kepler-7's orbit.

From the looks of it, the only planet in the system.