We can’t travel to other stars yet – and maybe we never will. But other residents of the solar system can tour the galaxy. At the same time, former residents of other star systems can visit our own. In fact, the Sun and its close neighbors might even swap planets.

Astronomers discovered a new comet earlier this year. They found that the comet had passed close to the giant planet Saturn a couple of years ago. Saturn’s gravity had given the comet a strong enough kick to escape the solar system and head for interstellar space. Another comet was ejected, in 1980, by the even bigger planet Jupiter.

Over the past decade, we’ve seen two asteroids from other star systems pass close to the Sun. They were moving fast enough to barrel through the solar system and keep on truckin’.

We might even get visits from planets. A recent study found that there are two gravitationally stable zones on the outskirts of the solar system – up to 3.8 light-years from the Sun. If a “rogue” planet – one that doesn’t orbit another star – drifted through one of these zones, it might be captured by the Sun. But the Sun’s grip wouldn’t be very strong. So if another star got close enough – say, Alpha Centauri, our closest neighboring system – it might pull the planet away. In fact, the two systems could even swap the planet back and forth – extending its tour of the galaxy.

More about traveling between stars tomorrow.

Script by Damond Benningfield