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NASA's two Voyager spacecraft explore a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. After more than 33 years of travel, the two Voyager probes will soon reach interstellar space, which is the space between stars. (NASA/JPL-Caltech)
Unexpected data from NASA’s Voyager 1 reveals the spacecraft could be closer to interstellar space than realized, now seemingly near the heliopause, the border of the heliosheath, which contains our solar system, and may actually be smaller than previously thought.
The probe’s low-energy charged particle instrument indicated a stagnation in the solar wind in December 2010 which has continued until at least February this year, believed to be a transition zone spanning from the edge of the solar system into interstellar space.
Stamatios Krimigis and his research team at the Johns Hopkins University (JHU) used data from Voyager 1 and Cassini’s magnetospheric imaging instrument’s ion and neutral camera, which examines streams of neutral atoms moving into our solar system from interstellar space.
"This tells us that Voyager 1 may be close to the heliopause, or the boundary at which the interstellar medium basically stops the outflow of solar wind," says Krimigis in a JHU press release.
"The extended transition layer of near-zero outflow contradicts theories that predict a sharp transition to the interstellar flow at the heliopause—and means, once again, we will need to rework our models," he added.
Scientists believe the probe has not yet crossed over, but is still traveling through the heliopause. The transition would be marked by a sudden drop in the density of the heliosheath’s hot particles and a subsequent increase in the density of the interstellar plasma’s cold particles.
The researchers were able to estimate the boundaries between the heliosphere and interstellar space, which are approximately between 10 and 14 billion miles from the sun. Already almost 11 billion miles out, Voyager 1 could cross over into interstellar space at any moment."These calculations show we’re getting close, but how close?" said Ed Stone at the California Institute of Technology in Pasadena, in a NASA press release.
"That’s what we don’t know, but Voyager 1 speeds outward a billion miles every three years, so we may not have long to wait."
The findings are published in the June 16 edition of Nature.
