The probe is set to become the third human-made object to leave the solar system, but it must first cross this mysterious boundary.

"All these discoveries from pioneering missions like Voyager and New Horizons teach us how little we know about what lies beyond."

New Horizons is often placed into a resource-saving mode while cruising long distances, and had been in hibernation near Pluto since August 7.

The probe is set to become the third human-made object to leave the solar system, but it must first cross this mysterious boundary.

The probe is six billion miles from Earth