Data from Voyager 1, now more than 11 billion miles (18 billion kilometers) from the sun, suggest the spacecraft is closer to becoming the first human-made object to reach interstellar space.
Research using Voyager 1 data and published in the journal Science on June 27 provides new detail on the last region the spacecraft will cross before it leaves the heliosphere, or the bubble around our sun, and enters interstellar space. Three papers describe how Voyager 1’s entry into a region called the magnetic highway resulted in simultaneous observations of the highest rate so far of charged particles from outside heliosphere and the disappearance of charged particles from inside the heliosphere.
Scientists have seen two of the three signs of interstellar arrival they expected to see: charged particles disappearing as they zoom out along the solar magnetic field, and cosmic rays from far outside zooming in. Scientists have not yet seen the third sign, an abrupt change in the direction of the magnetic field, which would indicate the presence of the interstellar magnetic field.
Scientists do not know exactly how far Voyager 1 has to go to reach interstellar space. They estimate it could take several more months, or even years, to get there. The heliosphere extends at least 8 billion miles (13 billion kilometers) beyond all the planets in our solar system. It is dominated by the sun’s magnetic field and an ionized wind expanding outward from the sun. Outside the heliosphere, interstellar space is filled with matter from other stars and the magnetic field present in the nearby region of the Milky Way.
Voyager 1 and its twin spacecraft, Voyager 2, were launched in 1977. They toured Jupiter, Saturn, Uranus and Neptune before embarking on their interstellar mission in 1990. They now aim to leave the heliosphere. Measuring the size of the heliosphere is part of the Voyagers’ mission.
The animations below 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. (It might take a while to load)
Before Voyager 1 reached the magnetic highway, charged particles bounced around in all directions, as if trapped on local roads inside the heliosphere, as shown in the first scene. The pink particles are the lower-energy charged particles that originate from inside the heliosphere, which is the bubble of charged ions surrounding our sun. The second scene shows Voyager entering the highway region, where inside (pink) particles zip away and particles from interstellar space (blue) stream in. These interstellar particles are called cosmic ray particles and have more energy than the inside particles. In the third scene, further travel through the magnetic highway means that all of the inside particles are leaving and the population of outside particles is much higher. The cosmic ray particles rapidly fill this new region to the same level as outside and speed in all directions. The fourth scene shows the point at which all of the inside particles have zipped out, leaving an area dominated by cosmic rays from outside.
These animations are based on data from Voyager 1’s cosmic ray instrument. These particles are invisible to the human eye and less populous, but are visualized here in exaggerated populations.
Bottom line: Data from Voyager 1, now more than 11 billion miles (18 billion kilometers) from the sun, suggest that after 35 years of travel, the spacecraft is close to becoming the first human-made object to reach interstellar space.
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