"It's going to be very difficult not having Mother Earth next to you," warns former astronaut Chris Hadfield.
The first exoplanet was detected in 1995, but the number has exploded in the last few years.
All seven roughly match the size and mass of our own planet and are almost certainly rocky.
The animal was found before Sunday's flight from Oman
The aircraft dating from the 1920s and 1930s took off on November 12 from the Greek island of Crete on their 13,000 kilometre (8,000-mile) journey to Cape...
Scientists say Planet Nine could have been cast off during the early formation of the solar system.