The science world has of late seemed particularly gloomy. Thanks to sequestration and the dysfunctional nature of Congress, funding for the NIH and NASA — two major pillars of American science research — has either been cut or is facing cuts. But on Sept. 12 NASA officially declared an incredible scientific milestone: Voyager 1, a small, old spacecraft with a simple mission, became the first human-made object to leave the solar system. According to the article published in Science, Voyager 1’s actual departure occurred in August 2012, but determining that Voyager 1 had in fact left the solar system was not a trivial analysis. In fact, as recently as this past June, NASA scientists did not think Voyager 1 had made it out yet.
It turns out the solar system is not, as many of us think, just our planets — defining its boundary is complicated since neither the Sun’s light nor gravity’s effects ever completely go away. Instead, NASA defines the solar system’s boundary as where the solar plasma, or ionized gas radiated from the sun, effectively ends. Voyager 1 is currently in interstellar space where the plasma is at a higher density than it would be in the heliosphere — a region of charged particles around the Sun that includes the planets. The heliosphere actually extends well beyond even the former furthest planet Pluto. The very edge of the heliosphere is known as the heliopause, where the effects of the plasma from the Sun finally end. Voyager 1 does not have a sensor for plasma, so NASA had to use a different strategy to determine the spacecraft’s actual position. A solar flare in March 2012 finally reached Voyager 1 in April 2013 and the ensuing oscillations of the plasma around the spacecraft indicated a higher gas density than would be found in the heliosphere, proving that Voyager 1 had in fact left our solar system.
Voyager 1 and its sister space craft Voyager 2, the two longest continuously operated spacecraft, were both launched in 1977 — for those of us under age 36 looking for a relatable cultural reference, it was, appropriately, the same year that Star Wars Episode IV: A New Hope opened. At the time, NASA was still in a Space Age high. Voyager 2 currently remains in the solar system but it too will eventually make it out (though in a different direction). The original purpose for the Voyager crafts was to roam around Jupiter, Saturn, Uranus and Neptune for a few years taking photos. The Voyagers revealed that Jupiter has rings (not as impressive as those of Saturn, but still), that one of its moons, Io, had volcanoes and that Saturn’s largest moon, Titan, had an Earth-like atmosphere. Among the many famous images the Voyagers took of space, perhaps the best-known is “The Pale Blue Dot” — a photo of Earth taken by Voyager 1 when it was well past Pluto in the periphery of the solar system. That photo, part of a “Family Portrait” series of the solar system as Voyager 1 looked back on all the planets, inspired a book by the astronomer (and member of the Voyager team) Carl Sagan, who wrote “There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny planet.”
In an age where we feel compelled to replace our laptops and smartphones every few years, it is impressive that the old-fashioned technology on the Voyagers is still working (maybe Apple can take some notes). NASA scientists predict that Voyager 1 will stop sending us information around 2025, when its power supply is expected to (finally) go kaput. They hope to learn more about interstellar space in the remaining years that Voyager 1 can communicate with us. But even after Voyager 1 stops transmitting messages to us, it can still serve a unique purpose, one that seems less laughable now than it might have in 1977: it contains a disc full of Earthling photos, greetings from world leaders and samples of our music so that E.T. can learn a little about us. Human history has seen many explorers, who we celebrate for their courage and determination. Voyager 1 and the team of scientists who have stuck by it deserve the same credit.