Seasoned space traveller Voyager 2 has surprised scientists as it approaches the edge of the solar system with data that shows the solar system to be oblong shaped, not spherical as previously thought.
Image: Artist\'s impression of Voyager. Credit: NASA
Originally launched in 1977, Voyager 2 last August reached the edge of the Sun's influence -- known as the heliosphere -- and encountered the region known as the termination shock where the solar wind slams into cold interstellar space. The area extends out past Pluto, which orbits the Sun at a distance of around six billion kilometres (four billion miles).
A report in the British journal Nature has said because Voyager 2 had a number of encounters with the shock, the original theory of the heliosphere being round is incorrect, with the discovery that it is much more oblong. The fact that the craft encountered the shock several times indicates the region is constantly in a state of flux, not static as previously thought.
“...the shock is not the steady structure that is predicted by the simplest theory,” says Len Burlaga of NASA’s Goddard Space Flight Centre in Greenbelt, Md. “It is like a wave approaching a beach, that grows, breaks, dissipates, and then re-forms closer to shore.”
Its twin, Voyager 1, crossed the same threshold some four years earlier at a different juncture.
Explaining the termination shock, University of Arizona Professor J. Randy Jokipii said in a UA statement last year: "Termination shocks are not unique to the heliosphere.You can see one in water running in your kitchen sink. The streaming water initially radiates outward faster than waves can propagate through it. As a result, the surrounding fluid cannot send an inward signal that its motion has been slowed. A shock front forms where the fast- and slow-moving parts of the fluid abruptly collide."
Saying crossing the heliosphere "opens a new age of exploration" Prof. Jokipii added. "The stream of in situ and remote data from the outer reaches of the heliosphere has revolutionized our view of how the Sun interacts with the Galaxy."
Looking to the future he said the real test will come when the craft begin exploring interstellar space.
"The Holy Grail for me will be when the spacecraft begin traveling in pure interstellar space," Jokipii said. "That's maybe 10 years away. Scientists now can start thinking about what they want to look for when the Voyagers break through the last barriers to true interstellar space."
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