Most of your students will have seen images of astronauts in films, television shows or books. To start out your study of space, bring in an astronaut doll or puppet. If you can't find one from a local toy store, you can dress up any puppet or stuffed animal to resemble an astronaut by making a makeshift helmet out of paper-mache. Put a white doll's shirt on the stuffed animal and put a sticker of an American flag on the front. During circle time, tell the students that you have a guest today. Bring out the astronaut and invite each student to ask one question.
To bring your study of space outside to the playground, organize a special obstacle course around the theme. Have students hop as far as they can as a "moonwalk" activity. Hang aluminum foil pie plates from the monkey bars and then challenge the students to cross them without hitting any of the dangerous "asteroids." Draw a large solar system on the ground with chalk and let students pass from one planet to another if they can answer trivia questions correctly.
Create fun coloring pages using different space-related items. To tie the coloring pages into learning about letters, make them part of a larger, year-long alphabet book project. For example, you might make coloring pages for astronauts, the moon, the sun, stars, or the universe. When doing a coloring page for "moon," the student would get to color a picture of the moon and would trace and copy a large "M."
You can adapt many common playground games to fit a space theme. For example, you can substitute "Duck, duck, goose" with "Astronaut, astronaut, alien." Instead of playing tic-tac-toe, create a large version of the game using pictures of the sun and moon. Divide the class into two teams and let students take turns coming up to place a sun or a moon on the board. For a simple racing game, you can create balloon rockets; affix two strings across the length of the classroom, horizontally. Thread each one through a single drinking straw. Inflate two balloons and tape one securely to each straw, keeping the balloon's opening pinched shut. Let one student hold each balloon and then, on the count of three, let it go. The air exiting the balloon will propel it across the room.