Answer : The radioisotope which has longest half-life and can be best to be used in powering planet and space exploration vehicle and travel farther will be Plutonium - 239 as it has the half life of 24065 years. Which in comparison to other radioisotopes is longest.
Hence, Plutonium - 239 can be the best suitable radioisotope for powering the planet and space exploration vehicle to travel farther.
