Is there life on other planets? If so, does it look like the monstrous thing Sigourney Weaver battled in the “Alien” movie blockbusters? Could you kiss it the way Captain Kirk was so fond of doing on “Star Trek”? Or, could it be related to your house plant? Students are grappling with such lively questions in “Astrobiology: The Search for Life in the Universe,” a course being piloted at Leicester, West Springfield, and 23 other high schools and middle schools nationwide.