On December 10, the Voyager 2 probe became the second man-made object to leave our solar system, crossing the barrier between the sun’s area of influence and the wilds of interstellar space. Only its sister probe, Voyager 1, has made this journey before.
Our sun is a gigantic nuclear power plant, generating colossal amounts of energy that it radiates into space around it. That energy warms planets like Earth, but it also repels the energy put out by other stars and interstellar objects. This creates a bubble called the heliosphere, an area around the sun that’s under its influence, protected from interstellar rays. (The sun’s powerful gravity extends out a bit further, though.
