Voyager 1 at the final frontier

June 22, 2012 by Dr. Tony Phillips, NASA
A sharp increase in cosmic rays could herald Voyager 1's long-awaited breakthrough to interstellar space.

For nearly 35 years, NASA’s Voyager 1 probe has been hurtling toward the edge of the solar system, flying through the dark void on a mission unlike anything attempted before. One day, mission controllers hope, Voyager 1 will leave the solar system behind and enter the realm of the stars—interstellar space.

That day may be upon us.

"The latest data from 1 indicate that we are clearly in a new region where things are changing quickly," says Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. This is very exciting. We are approaching the solar system's final frontier."

The “frontier” he’s referring to is the edge of the heliosphere, a great magnetic bubble that surrounds the sun and planets. The heliosphere is the sun’s own magnetic field inflated to gargantuan proportions by the solar wind. Inside lies the solar system—“home.” Outside lies interstellar space, where no spacecraft has gone before.

A telltale sign of the frontier’s approach is the number of cosmic rays hitting . Cosmic rays are high energy particles such as protons and helium nuclei accelerated to near-light speed by distant supernovas and black holes. The heliosphere protects the from these subatomic bullets, deflecting and slowing many of them before they can reach the inner planets.

As Voyager approaches the frontier, the number of cosmic rays has gone up.

"From January 2009 to January 2012, there had been a gradual increase of about 25 percent in the amount of galactic cosmic rays Voyager was encountering," says Stone.

"More recently, however, we have seen a very rapid escalation in that part of the energy spectrum. Beginning on May 7, 2012, the cosmic ray hits have increased five percent in a week and nine percent in a month."

The sharp increase means that Voyager 1 could be on the verge of a breakthrough 18 billion kilometers from Earth.

When Voyager 1 actually exits the heliosphere, researchers expect to see other changes as well. For one thing, energetic particles from the sun will become scarce as the spacecraft leaves the heliosphere behind. Also, the magnetic field around Voyager 1 will change direction from that of the sun’s to that of the new and unexplored magnetism of interstellar space.

So far, neither of these things has happened. Nevertheless, the sudden increase in suggests it might not be long.

Meanwhile, Voyager 2 is making its own dash for the stars, but because of its slower pace lags a few billion kilometers behind Voyager 1. Both spacecraft remain in good health.

"When the Voyagers launched in 1977, the Space Age was all of 20 years old," says Stone. "Many of us on the team dreamed of reaching , 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. "

As the Space Age nears the 55-year mark, there is little doubt: The Voyagers are going the distance.

This is a video version of the story.

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4 / 5 (2) Jun 22, 2012
I still think that NASA should engage a preliminary feasibility study to determine whether it is possible to send a probe toward
Voyager 1 or 2 in an effort to overtake them within the lifetimes of those who remember the time when they were launched. I think it is, and it would be a great test of the Variable Specific Impulse Magnetoplasma Rocket, which might be able to do the trip in about 10 to 15 years. It might be interesting to view images of how they would appear after 55 years in space.
4.7 / 5 (6) Jun 22, 2012
I remember a lot of talk, at least a decade ago, about sending a craft with an Ion thruster propulsion engine which would overtake the Voyager crafts before they reached the heliosphere. I wonder what happened to that?
not rated yet Jun 24, 2012
Yes, pictures of the two probes would be interesting. Unfortunately I just don't see the passion in our scientific endeavors nowadays like we saw back then. I do hope though that we see again soon the value of these programs like NASA.

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