Voyager 1 is even further out. It is over 103.6 AUs from the Sun, over 9.6 billion miles (15.5 billion meters) away. It is the furthest artificially made object that humans have ever launched into space. And it is traveling faster than any other object ever made.

Both spacecraft have not left the solar system yet, but are on journeys that will eventually let them leave the relatively safe confines of our solar system and enter interstellar space.

In December 2004, Voyager 1 crossed the termination shock (where charged particles of the solar wind slow down due to interactions with the oncoming particles and the magnetic field from the interstellar medium) into the heliosheath (the region where the solar wind slows down—the termination shock is its boundary).

At that time, Voyager 1 provided evidence to scientists that the solar system was asymmetrical.

The solar wind is composed of electrically charged particles blown out from the Sun that travel between 1 and 2 million miles per hour (1.6 to 3.2 million kilometers per hour) in all directions from the Sun.

The other side of the heliosheath is the heliopause, the point where the solar wind is stopped by the interstellar medium, and essentially the solar system ends and the interstellar medium begins. That boundary is called the bow shock.

Voyager 2 crossed the termination shock in August of 2007 (only a few billion miles from where Voyager 1 crossed the boundary) and confirmed what its sister ship had indicated. The solar system is indeed asymmetrical, and that irregularity is most likely due to disturbances in the interstellar magnetic field.

In fact, Voyager 2 found that the point where it crossed the termination shock was about one billion miles closer to the Sun that the point where Voyager 2 crossed the termination shock. These irregularities (or points where the solar system is “squashed” or “dented”) are caused by the interstellar magnetic field impinging on the uter boundary of the solar system.