Boom! Studio's website.
(Note that while many sites show Snoopy in an spacesuit on the cover, that appears to have been preliminary art that was changed. Tip of the hat to Previewsworld for the updated cover. Since Boom! Studios is publishing The Beagle Has Landed, a new Peanuts graphic novel with an space theme in October, no doubt they decided to save Snoopy as an astronaut for that book's cover.)