Voyager 1 Enters Final Region Of Our Solar System Before Interstellar Space

This artist's concept shows plasma flows around NASA's Voyager 1 spacecraft as it approaches interstellar space. Image Credit: NASA/JPL-Caltech/JHUAPL — This artist’s concept shows plasma flows around NASA’s Voyager 1 spacecraft as it approaches interstellar space. Image Credit: NASA/JPL-Caltech/JHUAPL

NASA’s Voyager 1 spacecraft, which left Earth some 35 years ago, continues on an epic journey across the solar system towards an inevitable crossing into interstellar space. The spacecraft has travelled farther than any man-made object ever has, and recent data sent from the spacecraft shows it is now pushing through a new region at the very edge of our known solar system, a “magnetic highway” that scientists feel is the final region before crossing into deep space.

This previously unknown (and unexpected) region at the edge of our solar system is where our sun’s magnetic field lines connect with the magnetic field lines of interstellar space, nicknamed by NASA as the “magnetic highway”. Low-energy charged particles from our solar bubble, known as the heliosphere, zoom out and allow higher-energy particles from interstellar space to zoom in. Before entering this region, the particles would zip around in all directions, but particles from deep space are now streaming over Voyager 1 regularly, something that has not been seen consistently before.

The new data alone does not suggest Voyager 1 has reached interstellar space because the direction of the sun’s magnetic field lines has not yet changed, but the data does show the region Voyager 1 is traveling through is rapidly changing. The influence of the sun is becoming less and less, while the influence from interstellar space is growing stronger.

VIDEO: This set of animations show NASA’s Voyager 1 spacecraft exploring a new region in our solar system called the “magnetic highway.” In this region, the sun’s magnetic field lines are connected to interstellar magnetic field lines, allowing particles from inside the heliosphere to zip away and particles from interstellar space to zoom in. Video Credit: NASA/JPL-Caltech

“Although Voyager 1 still is inside the sun’s environment, we now can taste what it’s like on the outside because the particles are zipping in and out on this magnetic highway,” said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. “We believe this is the last leg of our journey to interstellar space. Our best guess is it’s likely just a few months to a couple years away. The new region isn’t what we expected, but we’ve come to expect the unexpected from Voyager.”

“If we were judging by the charged particle data alone, I would have thought we were outside the heliosphere,” said Stamatios Krimigis, principal investigator of the low-energy charged particle instrument, based at the Johns Hopkins Applied Physics Laboratory, Laurel, Md. “But we need to look at what all the instruments are telling us and only time will tell whether our interpretations about this frontier are correct.”

Launched in 1977 on a Titan IIIE rocket from Cape Canaveral Air Force Station in Florida, the spacecraft is currently speeding through the cosmos at over 38,000 miles-per-hour. Voyager 1 is over 11 billion miles away from Earth. The distances Voyager 1 has covered are so vast that astronomers do not actually measure them in miles, but in Astronomical Units, or AU. One AU is the average distance between the Earth and Sun, about 93 million miles. Voyager 1 is currently over 123 AU from Earth, or 123 times further from Earth than Earth is from the Sun, and clearing over 3 AU every Earth year (365 days). At these distances, radio signals from Voyager 1 take over seventeen hours to reach researchers here on Earth, and the round-trip light time from the sun is over thirty-four hours.

This artist’s concept shows NASA’s two Voyager spacecraft exploring a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. Image credit: NASA/JPL-Caltech

Voyager 1 crossed through an area known as the “termination shock” and began its voyage through the heliosheath in December of 2004. The heliosheath is the outer boundary of our solar system still dominated by the sun’s magnetic field and particles contained in the solar wind. Although astronomers don’t know exactly just how wide the heliosheath is, and therefore cannot pinpoint exactly where the border between our solar system and interplanetary space is, they can see changes in the environment become more dramatic as Voyager 1 approaches the border, known as the heliopause.

In the eight years since Voyager 1 began its treck through the heliosheath, the spacecraft has encountered several dramatic changes in its space environment—all pointing to its eventual exit from our solar system into interstellar space. The number of cosmic rays hitting the spacecraft continues to climb, and instruments on the spacecraft detected the supersonic solar wind dropped from 150,000 mph to zero as of last spring—held back from further expansion by the interstellar wind. Over the last year the spacecraft has also seen energetic particles from the solar system decline by nearly 50 percent, while the detection of high-energy electrons from interstellar space has increased 100 fold.

540354main_voyager20110427-full — The Voyager Program is comprised of two separate spacecraft, each of which have opened up mankind’s understanding of space. Image Credit: NASA

“We are in a magnetic region unlike any we’ve been in before—about 10 times more intense than before the termination shock—but the magnetic field data show no indication we’re in interstellar space,” said Leonard Burlaga, a Voyager magnetometer team member based at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock. And we expect these data will tell us when we first reach interstellar space.”

This artist's concept shows the different expected directions of the magnetic fields in interstellar space (black lines) and the magnetic field emanating from our sun (white lines). Image Credit: NASA/JPL-Caltech — This artist’s concept shows the different expected directions of the magnetic fields in interstellar space (black lines) and the magnetic field emanating from our sun (white lines). Image Credit: NASA/JPL-Caltech

Although Voyager 1 is still in an environment dominated by the sun’s magnetic field, researchers expect to see the spacecraft exit the heliosphere sometime between now and 2015. When that occurs, big changes are expected to be seen in the data sent back to Earth. For example, energetic particles from the sun will be few and far between, and the magnetic field around Voyager 1 will change direction from that of the sun’s magnetic field to that of the unexplored magnetism of interstellar space.

The Earth as photographed by Voyager 1 at a distance of 4 billion miles from home on Valentines Day, February 14, 1990. Famed astronomer Carl Sagan called named this image the “Pale Blue Dot”, saying in a speech in 1994 that “all of human history has happened on that tiny pixel, which is our only home.” Photo Credit: NASA — The Earth as photographed by Voyager 1 at a distance of 4 billion miles from home on Valentine’s Day, February 14, 1990. Famed astronomer Carl Sagan named this image the “Pale Blue Dot,” saying in a speech in 1994 that “all of human history has happened on that tiny pixel, which is our only home.” Photo Credit: NASA

Although traveling slower, and thus lagging behind its cousin Voyager 1, Voyager 2 is currently traversing the solar system on a course which will eventually see it leave the solar system as well. Both spacecraft are reported to be in good health, and have enough power and thruster fuel to operate until at least 2020, possibly until 2025.

The twin Voyager spacecraft should provide better data regarding what the space between stars and solar systems is like in a way no other spacecraft has ever been able to, simply because no spacecraft has ever actually travelled there. Originally Voyager 1 and 2 were to explore the gas giant planets in the outer solar system—Voyager 2 is still the only spacecraft to have ever visited Uranus and Neptune. Their current mission, the Voyager Interstellar Mission (VIM), aims to extend our exploration beyond the solar system.

“When the Voyagers launched in 1977, the Space Age was all of 20 years old,” said Stone. “Many of us on the team dreamed of reaching interstellar space, but we really had no way of knowing how long a journey it would be — or if these two vehicles that we invested so much time and energy in would operate long enough to reach it. This is very exciting. We are approaching the solar system’s final frontier.”