Friday, July 20, 2012
Scientists have finally cracked a decades-old spaceflight riddle, figuring out why NASA’s Pioneer 10 and 11 probes began to slow mysteriously as they sped far from the sun.
The cause of the so-called “Pioneer Anomaly,” it turns out, is heat coming from the electrical current flowing through the probes’ instrument and power systems. This heat pushed back on the spacecraft, causing them to decelerate slightly, according to a new study.
“The effect is something like when you’re driving a car and the photons from your headlights are pushing you backward,” lead author Slava Turyshev, of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., said in a statement. “It is very subtle.”
Pioneer 10 and Pioneer 11 launched in 1972 and 1973, respectively. They were the first spacecraft to fly through the main asteroid belt, and the first to study Jupiter up-close. The probes kept on cruising after their Jupiter encounters, speeding toward Saturn and beyond.
Pioneer 10 and 11 will eventually exit the solar system, but they likely won’t be the first to do so. Scientists think the Voyager 1 spacecraft, which is about 11.1 billion miles (17.8 billion kilometers) from Earth, may leave our cosmic neighborhood any day now.