"Everyone's been asking, 'Where did the energy go? Where did the energy go?' " said Krimigis "Now we know."
Solar wind shoots from the sun like water flowing into a pan from a tap, radiating outward until it reaches a turbulent edge.
When Voyager reached termination shock last August, its detectors showed the same effect as water in a sink, with hydrogen particles from space slowing down the solar wind and robbing it of heat.
"These hydrogen ions dominate what happens out there," said Decker, an APL physicist since 1980.
The two Voyager probes were designed to last just five years when NASA launched them in 1977 to study Jupiter, Saturn, Uranus and Neptune. But they were still operating in 1990, when NASA sent them on to explore the solar system's outer reaches.
Voyager 1 had a central role in the first Star Trek movie, released in 1979. In the film, the probe is a menacing interstellar force known to the starship's crew as the mysterious "V'GER." Its identity becomes clear only at the end of the movie.
Voyager 1 passed through the termination shock in late 2004, heading out of the solar system in a different direction. But its data were not as precise - astrophysicists debated whether the probe had reached the edge of the solar system or was still a year away. Voyager 2 answered many of their questions.
Engineers say the plutonium power generators on the twin probes could keep them in business till 2020.
"They could be making discoveries another 10 years or longer," Krimigis said. "We'll just to have to wait and see."
dennis.obrien@baltsun.com
