This is book number 24 in the Little Prince series.
The Little Prince and Fox fly back and forth across space to save planets before the Snake can destroy them. But this time, it's the Little Prince's Asteroid B612 that has been menaced: the Rose was kidnapped by his enemy The Little Prince sets out for the Planet of the Snake, guided by the friends he made during his travels. But in the Snake's murky realm, the Little Prince will only be able to count on his courage and Fox's friendship. Will the Prince succeed in saving his Rose and vanquishing the Snake once and for all?