By changing his material body birth after birth, he (the living entity) travels not only in the different species of life, but also from one planet to another
SB Canto 3
Due to his particular type of body, the materialistic living entity wanders from one planet to another, following fruitive activities. In this way, he involves himself in fruitive activities and enjoys the result incessantly.
When the living entity is encaged in the material body, he is called jīva-bhūta, and when he is free from the material body he is called brahma-bhūta (SB 4.30.20). By changing his material body birth after birth, he travels not only in the different species of life, but also from one planet to another. Lord Caitanya says that the living entities, bound up by fruitive activities, are wandering in this way throughout the whole universe, and if by some chance or by pious activities they get in touch with a bona fide spiritual master, by the grace of Kṛṣṇa, then they get the seed of devotional service. After getting this seed, if one sows it within his heart and pours water on it by hearing and chanting, the seed grows into a big plant, and there are fruits and flowers which the living entity can enjoy, even in this material world. That is called the brahma-bhūta stage. In his designated condition, a living entity is called materialistic, and upon being freed from all designations, when he is fully Kṛṣṇa conscious, engaged in devotional service, he is called liberated. Unless one gets the opportunity to associate with a bona fide spiritual master by the grace of the Lord, there is no possibility of one's liberation from the cycle of birth and death in the different species of life and through the different grades of planets.