NASA is redrawing models of our solar system as their Voyager 1 spacecraft reaches the cusp of interstellar space ahead of schedule.
But this isn’t the first time the Voyagers have disrupted scientific prediction and theory. Launched in the summer of 1977, the Voyager 1 and Voyager 2 were originally intended for four-year missions to observe Saturn and Jupiter. “But [they’re] still returning data 33 years later,” says Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena.
Here’s a few of the probes’ textbook-changers from over the years.
- The two Voyagers worked in unison with one another to discover actively erupting volcanoes on Jupiter’s moon “Io,” as well as rifts and kinks in Saturn’s rings from the gravitational pull of the planet’s moons. In 1980, with the original mission complete, the Voyager 2 continues onward while Saturn’s pull curves the Voyager 1’s trajectory away from the ecliptic, or the plane on which most planets orbit the sun.
- To take advantage of a planetary alignment that happens once every 176 years, the Voyager 2’s mission was updated to fly by and explore Uranus in 1986 and Neptune in 1989, discovering Neptune’s Great Dark Spot and 1,000-mile-per-hour winds and geysers erupting from the nitrogen ice that forms the polar cap of the planet’s moon “Triton.”
- In December of 2004, the Voyager 1 left the heliosphere – the solar wind bubble – and entered the heliosheath, the outer shell of our sun’s sphere of influence. Travelling at 38,000 mph to Voyager 2’s 35,000 mph and in different directions, the real surprise came when the Voyager 2 did the same in 2008. This proved the heliosphere isn’t a sphere at all, but instead an oblate spheroid (eggish).
- June 2010, NASA scientists realized the solar winds emanating from the sun against the Voyager 1 had slowed to a halt. This means the craft is now far enough out – about 10.8 billion miles from the sun – that interstellar wind in the space between stars has greater influence on the vessel than our sun. “The solar wind has turned the corner,” says Stone. “Voyager 1 is getting close to interstellar space.”
Scientists waited for four more monthly readings before they were convinced the solar wind’s outward speed actually had slowed to zero. It has remained at zero since June, proving the heliosheath to be thinner than predicted.
The current mission of Voyagers is to reach the edge of interstellar space, which they estimate the Voyager 1 will do within the next four years.