Extrasolar planets are planets that orbit a star that is not our sun. They are often lightyears away and astronomers study them using spectroscopy and other methods to determine where the planets are.
Space weather is how the environment around the Earth and solar system may vary because of activity at the sun. The Northern Lights is a harmless example of space weather. It is an effect of an event called a Coronal Mass Ejection or CME.
Scrat accidentally enters a flying saucer and propels himself into outer space. He travels through the solar system (also by accident), and during his journey finds a solar system, planets, asteroids, and other celestial objects.