NASA's Voyager 1 spacecraft, launched in 1977, has left our solar system, to become the first man-made object to enter interstellar space. New data shows that the craft is presently traveling through plasma, the ionized gas that makes up the space between stars, roughly 12 billion miles from the sun.
NASA reports that the probe had entered the plasma region about a year ago, though is in a transitional area, to where the effects of our sun are still present. Ed Stone, a Voyager project scientist based at the California Institute of Technology, Pasadena, says, "now that we have new, key data, we believe this is mankind's historic leap into interstellar space. The Voyager team needed time to analyze those observations and make sense of them. But we can now answer the question we've all been asking, 'Are we there yet?' Yes, we are."
The Voyager craft doesn't have a plasma sensor, so scientists had to get creative in order to figure out what sort of environment it was in. In March, 2012, the sun emitted a burst of solar wind and magnetic fields called a coronal mass ejection, giving scientists what they'd needed to get a general idea of the craft's position. It took 13 months for this burst to hit Voyager, and on April 9, the probe's plasma wave instrument showed the density of the plasma in the space it was in - about 40 times more dense that what was previously gauged in the outer layer of the heliosphere.
The analysis of the new data was conducted by the plasma wave science team at the University of Iowa, led by Don Gurnett. "We literally jumped out of our seats when we saw these oscillations in our data - they showed us the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble," Gurnett said, adding, "clearly we had passed through the heliopause, which is the long-hypothesized boundary between the solar plasma and the interstellar plasma."
When Voyager 1 was launched decades ago, it's primary objective was to obtain detailed images from the Jovian and Saturnian systems, which was accomplished in 1980. Presently, the nuclear-powered craft is traveling at about 11 miles per second, and likely won't be able to power any of its instruments by 2025. The craft is loaded with a gold-plated disc full of audio and visual information, in case any sentient beings from other planets come across it. The disc includes pictures of earth and earthlings, various sounds including whale calls and baby cries, and music by Mozart and Chuck Berry. The scientific information included also kindly gives aliens pointers on how to more easily defeat us.