On Monday, December 10th, NASA’s Voyager 2 spacecraft became the second ever human-made object to leave the heliosphere and reach interstellar space.

With the main motive being to research outer planets, Voyager 2 visited Jupiter, Saturn, Uranus, and Neptune, becoming the only spacecraft to reach every gas giant planet. The probe contributed to various astronomical discoveries, including that of Neptune’s Great Dark Spot and cracks in the Europa moon’s ice surface.

As a part of the Voyager program, the spacecraft was launched on August 20th, 1977, and studied the solar system for 41 years. During this time, Voyager 2 covered a distance of approximately 17 billion kilometers and is moving at a rate of 54,000 kilometers per hour.

In regards to the probe, principal investigator for the Voyager 2’s “Plasma Science Instrument” (PLS), John Richardson, stated, “Even though Voyager 1 crossed the heliopause in 2012, it did so at a different place and a different time, and without the PLS data. So we’re still seeing things that no one has seen before.”