To ease your worries, there are entire teams dedicated to the observation of asteroids and their potential risk to our planet. Plus the testing of planetary defense systems has had notable results, even if it was just a test against a non-threatening object. In terms of stars and other interstellar objects... The threat to our planet is, at worst, extremely miminal. Most supernovae candidates are at a relatively safe distance from us. And the chance of an exo-planet or star swinging through our solar system is practically non-existent.

The biggest threat to the planet is living on the planet... They're these weird, bipedal creatures called "humans."