WASHINGTON (Reuters) - Voyager 2, a NASA probe launched in 1977 and designed for just a five-year mission, has become only the second human-made object to enter interstellar space as it continues its marathon trek billions of miles (km) from Earth, scientists said on Monday. Since information takes about 16.5 hours to travel from the spacecraft to Earth–even moving at the speed of light–scientists figured out that the probe crossed the outer edge of the heliosphere on November 5, thereby crossing over into an area of space known as the heliopause, which the NASA press office poetically describes as the place where “the hot solar wind meets the cold, dense interstellar medium.”

Space enthusiasts will remember that Voyager 1 crossed the heliopause in 2012, however Voyager 2’s passage is remarkable because it is outfitted with instruments like a cosmic ray subsystem and a magnetometer that will provide first-of-its-kind observations about the nature of interstellar space. For only the second time in recorded history, humans have sent a spacecraft outside the heliosphere, the protected circle of particles and magnetic fields created by the Sun, and presumably Matthew McConaughey (ho-yay, Interstellar joke) . While the probes have left the heliosphere, Voyager 1 and Voyager 2 won’t leave the solar system for some 300 years, as it extends beyond the outer edge of the Oort Cloud, a fact that is being included only because it’s fun to write the word Oort. According to NASA, Voyager’s Plasma Science Experiment (PLS), which stopped working on Voyager 1 back in 1980, “uses the electrical current of the plasma to detect the speed, density, temperature, pressure and flux of the solar wind,” giving scientists their first hint of what’s happening inside and now outside the heliosphere. Both were designed as five-year missions to study Jupiter and Saturn up close, and when those were successful, flybys were added for Uranus and Neptune.
NASA announces that Voyager 2 entered into the interstellar medium after exiting the heliosphere on November 5.