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March 20, 2013
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Credit: Jen Christiansen
Tracking the location of the Voyager 1 spacecraft can be exhausting for a science journalist, and I can only imagine how confusing it gets for the interested reader. The relevant question pertaining to Voyager 1’s location is this: Has the venerable NASA spacecraft exited the heliosphere, the sun’s plasma cocoon in space, and crossed into the interstellar medium? The answer has swung for years between variations on “no” and “maybe,” most recently landing on “not yet” when mission scientists unveiled the latest data from the probe in a December teleconference.
So a press release this morning from the American Geophysical Union, proclaiming that “Voyager 1 has left the solar system,” caught my attention. (The headline was later revised to state that “Voyager 1 has entered a new region of space.”) The gist of the release: a new study in Geophysical Research Letters, analyzing cosmic ray data from Voyager 1, concludes that the probe “appears to have travelled beyond the influence of the Sun and exited the heliosphere.” On August 25, 2012, Voyager 1 registered a precipitous drop in local cosmic rays (charged particles accelerated to high energies) and an increase in cosmic rays from interstellar space.
The data are intriguing, but the interpretation is problematic. Voyager project scientists have been aware of the August changeover for months and have already offered more mundane explanations for the cosmic-ray data. “Voyager has discovered a new region of the heliosphere that we had not realized was there,” Voyager project scientist Ed Stone of the California Institute of Technology said in December. “We’re still inside, apparently.”
Credit: NASA
At that time, the researchers noted that the particle data were indeed compelling but that magnetic-field data from Voyager 1 had not yet registered the kind of change expected at the boundary of the heliosphere. “If we had only looked at particle data alone, we would have said, ‘Well, we are out. Goodbye to the solar system,’” said Tom Krimigis of the Johns Hopkins University Applied Physics Laboratory.
The Geophysical Research Letters study does just that—it looked at the particle data alone—so its conclusions should be taken with an interstellar grain of salt. And it is worth noting that the paper is somewhat more cautiously worded than its accompanying press release, claiming only that the boundary Voyager 1 crossed in August is “possibly related to the heliopause,” or the edge of the heliosphere.
In any case, a more comprehensive look at the boundary is forthcoming—studies from three instruments on Voyager 1, including the magnetometer, have been submitted to the journal Science. A Voyager scientist contacted today said that his team had not been informed about the preemptive Geophysical Research Letters paper.
Voyager 1 has ventured farther from Earth in its 35 years than any other man-made object, and when it does leave the heliosphere it will offer humankind our first taste of interstellar space. Given the importance of that accomplishment, I will await official word on Voyager 1’s location—as exhausting and confusing as waiting can be.
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The strength and direction of the galactic / interstellar magnetic field is probably not uniform over time. In addition, since the Sun is exiting a solar minima and its magnetic activity is increasing, this may cause the heliopause to expand further away over the period of months to years. Voyager 1 may have entered a transition zone that has now expanded because of increasing solar activity, or it initially crossed the heliopause only to be surpassed by the barrier some time later, confusing the scientists studying the issue. Just a thought.
Link to thisJohn I really appreciate that you check these types of claims & do not rush to uncritical acceptance.
Link to thisThe interpretations of the solar wind will be complicated if the sun has a companion star.
Link to thisIt doesn’t
Link to thisWhy do you say Voyager 1 has not left the heliosphere? We don’t know! Why do we have to be so ultra conservative. I call this the puppy dog effect. We are too scared to speak our minds we tend pander to the egos of the few who hold back ubiquitous advancement of science. Have some guts!
Link to thisHow fast has Voyager 1 been slowing down as it gets further away from the Sun? Past Neptune it probably was going at X speed and slowing down at Y rate per second per second. I would imagine that it is going at some slower speed but not slowing down so fast being further away from the Sun. Where is it in relation to the Oort Cloud? I realize that not much is known about Oort to give a good answer. I wonder how many Oort or other objects are in interstellar space just drifting with the flow.
Link to thisI’d say we’re currently standing on giants’ shoulders – except we fell off quite some time ago.
At least those of us interested in space exploration aged 50 and up got a taste of the real deal in real time, all those years ago. And, as it turns out, we and our younger cohort can still be amazed, thanks to the ingenuity of the old NASA and the durability of its hardware.
Thanks for the memories, old timers!
Link to thisThe old Nasa was extremely cool the new Nasa seems to be full of spin doctors. I can smell Bull a mile away.
Link to thisHow about some miles from the sun and AU distances and total miles traveled and the like? Also how much of a light year has it traveled? If it has been going fast I could see 0.3% of a light year. I wouldn’t buy a claim of a full 1% of a light year though.
If we get a base established on the moon with pusher lasers we may get up to a 1% speed of light velocity for a while. Maybe it would be able to go fast enough to cut the travel time to another star to mere decades instead of centuries. That would make a probe to another star a possible long term project.
Link to thisThe return of Voyager, now known as V’ger was interrupted by the Star Ship Enterprise. We are currently unaware of its location.
Link to this