NASA Voyager 2 could be nearing interstellar space

NASA Voyager 2 could be nearing interstellar space
This graphic shows the position of the Voyager 1 and Voyager 2 probes relative to the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. Voyager 1 crossed the heliopause, or the edge of the heliosphere, in 2012. Voyager 2 is still in the heliosheath, or the outermost part of the heliosphere. Credit: NASA/JPL-Caltech

NASA's Voyager 2 probe, currently on a journey toward interstellar space, has detected an increase in cosmic rays that originate outside our solar system. Launched in 1977, Voyager 2 is a little less than 11 billion miles (about 17.7 billion kilometers) from Earth, or more than 118 times the distance from Earth to the Sun.

Since 2007 the probe has been traveling through the outermost layer of the heliosphere—the vast bubble around the Sun and the planets dominated by solar material and magnetic fields. Voyager scientists have been watching for the spacecraft to reach the outer boundary of the heliosphere, known as the heliopause. Once Voyager 2 exits the heliosphere, it will become the second human-made object, after Voyager 1, to enter interstellar space.

Since late August, the Cosmic Ray Subsystem instrument on Voyager 2 has measured about a 5 percent increase in the rate of cosmic rays hitting the spacecraft compared to early August. The probe's Low-Energy Charged Particle instrument has detected a similar increase in higher-energy cosmic rays.

Cosmic rays are fast-moving particles that originate outside the solar system. Some of these cosmic rays are blocked by the heliosphere, so mission planners expect that Voyager 2 will measure an increase in the rate of cosmic rays as it approaches and crosses the boundary of the heliosphere.

In May 2012, Voyager 1 experienced an increase in the rate of cosmic rays similar to what Voyager 2 is now detecting. That was about three months before Voyager 1 crossed the heliopause and entered .

However, Voyager team members note that the increase in is not a definitive sign that the probe is about to cross the heliopause. Voyager 2 is in a different location in the heliosheath—the outer region of the —than Voyager 1 had been, and possible differences in these locations means Voyager 2 may experience a different exit timeline than Voyager 1.

The fact that Voyager 2 may be approaching the heliopause six years after Voyager 1 is also relevant, because the heliopause moves inward and outward during the Sun's 11-year activity cycle. Solar activity refers to emissions from the Sun, including solar flares and eruptions of material called . During the 11-year solar cycle, the Sun reaches both a maximum and a minimum level of activity.

"We're seeing a change in the environment around Voyager 2, there's no doubt about that," said Voyager Project Scientist Ed Stone, based at Caltech in Pasadena. "We're going to learn a lot in the coming months, but we still don't know when we'll reach the heliopause. We're not there yet—that's one thing I can say with confidence."

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Citation: NASA Voyager 2 could be nearing interstellar space (2018, October 5) retrieved 21 April 2019 from
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Oct 06, 2018
Voyager 1 crossed into interstellar space 121 AU from the Sun. Voyager 2 is currently 118.8 AU from the Sun and in three months time will be about 119.6 AU from the Sun. Interestingly, Voyager 2 has an active plasma science instrument, so it can directly detect the solar wind and we might learn a little more about crossing into interstellar space this time around. Voyager 1's is broken and that information had to be inferred.


Oct 06, 2018
Voyager 1 was undoobatably damaged by a lightning bolt fired at it by from an Official EU electricgun when the probe passed too close to the secret theosophist base on Planet Mysterion!

Shh, don't tell anybody.... It's suppose to be a secret. Part of the Uranus Conspiracy to suppress public knowledge of EU woowhooey.

And you thought the illuminati were even in this game? Bah! They haven't been serious players on the World scene since Benjamin Franklin and Napoleon Bonaparte whipsawed them to avenge the Assassination of Mozart!

Oct 06, 2018
I am glad that is official, saw someone meticulously following the published data on a site giving an opinion that 'maybe it is close' one or two weeks ago.

@Mark: Thanks for the roundup! I had forgotten that we may get nicer data (if the instrument keeps being supplied with enough power a few more months).

Oct 07, 2018
As a young lad, I loved the first Star Trek film - "Star Trek - the Motion Picture" and I watched old reruns of the TV show.
And it turns out that the Voyager or Vger in the movie was Voyager 6. I'm wondering now if there will ever be another Voyager besides these two. Perhaps equipped with enough nuclear fuel to last a million years.

Oct 08, 2018
Mark: Thanks! It will be good to get a second, fuller set of observations about the boundary of interstellar space.
rrwillsj: I'm thinking you pulled that out of you know where...
SEU: I like STTMP too. Our probes have to go much faster for V6 to reach the machine planet in reasonable time. (I'm not sure where Starman's civilization intercepted V2...) One of the ways we might communicate over interstellar distances with low power signals is to place relays at the solar focal points opposite the desired target. Our sun's focal point (actually an axis) begins at about 550 AU. Now consider that our voyagers are less than a quarter of the way the way to that distance despite having been outward bound since 1977. We're going to need some better tech to put observatories/relays at those focal points.

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