After 36 years and a journey that took the spacecraft 12 billion miles beyond the sun, Voyager 1 has left the solar system, the first human jaunt into interstellar space, U.S. scientists said.
The probe crossed into a region of cold, dark space outside the heliosphere, a bubble of charged particles at the boundary of the solar system, on Aug. 25, 2012, according to a report in the journal Science by researchers from the National Aeronautics and Space Administration and the University of Iowa.
Designed for just a four-year mission, Voyager is powered to operate until 2025. After flying past Jupiter and Saturn, it now takes 17 hours for Voyager’s signals to reach NASA’S Jet Propulsion Laboratory, the agency said.
“Voyager, like the ancient mariners, is pushing into new territory,” John Grunsfeld, NASA’s associate administer for the Science Mission Directorate, and a former astronaut, said yesterday in a news conference. “Someday humans will leave our cocoon in the solar system to explore beyond our home system. Voyager will have led the way.”
Data from Voyager indicate that the craft has been traveling through plasma, or ionized gas, which is found in the environment between stars, according to a statement from NASA.
Voyager’s plasma sensor broke, complicating the task of pinpointing its location. The plasma inside the heliosphere is hot, and highly charged. Outside, the denser, cooler plasma is made up of particles from explosions millions of years ago.
A massive burst of energy from the sun in March 2012 reached the Voyager 13 months later, causing the plasma around the craft to vibrate. The space craft picked up this movement, and the pitch of the vibrations helped scientists determine where the spacecraft was.
Voyager appeared to be in plasma more than 40 times denser than that at the outer edge of the heliosphere, the kind of density associated with interstellar space.
The signals from the spacecraft are very dim, with about the power of the refrigerator light bulb, NASA said. Scientists aren’t sure when Voyager 1 will reach the part of interstellar space that is undisturbed by the sun.
“We made it,” Ed Stone, a Voyager project scientist based at the California Institute of Technology, Pasadena, said during the press conference. “We still have enough power to send back home what we’re now exploring, this new region of space.”
The cost of Voyager 1 and Voyager 2, which is not far behind its younger sibling, has been about $988 million through September, according to NASA. Voyager 2 was launched 16 days earlier than Voyager 1, in 1977.
The study was led by Donald Gurnett, at the University of Iowa in Iowa City.