NASA today said its 36-year-old Voyager 1 spacecraft has officially become the first human-made object to enter into interstellar space.
For the past couple years scientists have been arguing whether or not the venerable spacecraft had in fact left our solar system or not. But in a press conference today Don Gurnett and the plasma wave science team at the University of Iowa said new data obtained around August 25, 2012 indicated Voyager had indeed moved into interstellar space.
"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.
"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, "said Ed Stone, Voyager project scientist based at the California Institute of Technology.
Calling it a truly alien environment, NASA said Voyager is in a region immediately outside the solar bubble, where some effects from our sun are still evident. The area is also known as the heliopause, which is the long-hypothesized boundary between the solar plasma and the interstellar plasma.
Scientists said they don’t know when Voyager 1 will reach the undisturbed part of interstellar space where there is no influence from the sun. They also are not certain when its sister ship, Voyager 2 is expected to cross into interstellar space, but they believe it is not very far behind. Voyager 1 and 2 were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft. It is about 9.5 billion miles (15 billion kilometers) away from our sun, NASA said.
NASA noted that Voyager 1 does not have a working plasma sensor, so scientists needed a different way to measure the spacecraft's plasma environment to make a definitive determination of its location. “A coronal mass ejection, or a massive burst of solar wind and magnetic fields, that erupted from the sun in March 2012 provided scientists the data they needed. When this unexpected gift from the sun eventually arrived at Voyager 1's location 13 months later, in April 2013, the plasma around the spacecraft began to vibrate like a violin string. On April 9, Voyager 1's plasma wave instrument detected the movement. The pitch of the oscillations helped scientists determine the density of the plasma. The particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. Density of this sort is to be expected in interstellar space.” NASA said.
Voyager mission controllers still talk to or receive data from Voyager 1 and Voyager 2 every day, though the emitted signals are currently very dim, at about 23 watts -- the power of a refrigerator light bulb.
By the time the signals get to Earth, they are a fraction of a billion-billionth of a watt, NASA said. Data from Voyager 1's instruments are transmitted to Earth typically at 160 bits per second, and captured by 34- and 70-meter NASA Deep Space Network stations. Traveling at the speed of light, a signal from Voyager 1 takes about 17 hours and 22 minutes to travel to Earth. After the data are transmitted to NASA’s Jet Propulsion Laboratory and processed by science teams and Voyager data are made publicly available.
NASA says it anticipates being able to communicate with Voyager for about 10 more years.
The cost of the Voyager 1 and Voyager 2 missions -- including launch, mission operations and the spacecraft's nuclear batteries, which were provided by the Department of Energy -- is about $988 million through September, NASA said.
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