Voyager 1 thought to be along the 'magnetic highway at edge of solar system

Spacecraft thought to be on edge of the solar system
2013-03-26T00:00:00Z 2014-07-22T11:16:12Z Voyager 1 thought to be along the 'magnetic highway at edge of solar systemTom Beal Arizona Daily Star Arizona Daily Star
March 26, 2013 12:00 am  • 

Faculty and graduate students at the UA's Lunar and Planetary Lab spent the noon hour Monday discussing the conflicting signals being sent by Voyager 1, which may become the first spacecraft to ever leave our solar system.

It may have already left the heliosphere formed by our sun, though scientists argue over whether it is still in a boundary called the heliopause or has left the solar neighborhood and entered interstellar space.

What's truly amazing is that this tiny spacecraft left Earth so long ago that it contains a message to unknown civilizations on a golden phonographic record, containing songs from Bach to Chuck Berry and a Navajo night chant, led by Sandoval Begay.

Launched on Sept. 5, 1977, Voyager 1 and its twin, Voyager 2, completed their primary science missions long ago, sending back the first close-ups of the gas giants in the outer solar system.

Our first notions of what Saturn, Uranus, Neptune, Jupiter and their moons really look like came from its cameras.

It is no longer taking pictures, but its three scientific instruments are measuring particles and magnetic waves, sending back clues to what space is like beyond the influence of our sun.

Voyager 1 may not have left the solar system, but it definitely ventured somewhere no spacecraft has ever gone before.

Over at the University of Arizona's LPL, where planetary scientists are engaged in any number of missions to targets within our solar system, the notion that we may have gone beyond that boundary was not so much debated as mused over on Monday as Vladimir Florinski visited from the University of Alabama to give his take on what the latest data from Voyager's 35-year mission mean.

Florinski, an assistant professor of physics at Alabama in Huntsville, studies data from Voyager on a NASA team that also includes LPL professor Randy Jokipii. They are two of thousands of engineers and scientists who have had a role in this venerable space project. According to NASA, the 11,000 work-years spent on the missions is about one-third the effort needed to build the great pyramid at Giza.

The data being analyzed now are nearly a year old, so what scientists were debating last week and continue to debate this week is not where Voyager is now, but where it was in June and August of 2012, when that data began showing a dramatic drop in the measurement of particles we'd expect to find within our sun's heliosphere and growth in the galactic cosmic rays that dominate the interstellar medium outside the sun's influence.

Only one thing was missing - a change in the direction of the magnetic field, predicted in theories about what we might find when the spacecraft does cross over.

Florinski, whose brown-bag colloquium was basically a job interview, said he wouldn't address the controversy directly, but he did offer some explanations for why we're seeing two and not three of the telltale signs of leaving the solar system.

Researchers had reported last week in the journal Geophysical Research Letters that the boundary had been crossed and the news release from the American Geophysical Union was unequivocal.

"Thirty-five years after its launch, Voyager 1 appears to have traveled beyond the influence of the sun and exited the heliosphere, according to a new study."

NASA's Jet Propulsion Laboratory, which funded the research, quickly denied that interpretation of the study, though it said the study itself was fine.

Its news release read: "It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space. In December 2012, the Voyager science team reported that Voyager 1 is within a new region called 'the magnetic highway' where energetic particles changed dramatically. A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed."

So what did happen?

Florinski said there was a "sharp transition" from particles you would expect to find in the heliosphere, the "bubble" created by our nearest star's solar wind, to those galactic cosmic rays you'd expect to find on the other side.

The magnetic field is the only contraindication, he said.

It could be that the heliopause, the place where the magnetic fields of the two regions meet up, is not a smooth region, but a "wavy, turbulent boundary," through which Voyager is now passing, he said.

Or Voyager could have crossed a different boundary created by the different directions of solar winds from the sun's north and south hemispheres.

Or maybe, one participant suggested after the talk, those magnetic field measurements, very weak, and very open to interpretation, are not what they seem to be.

We weren't supposed to be having this discussion yet.

Scientists had originally predicted that the distance to the heliopause would be 130 to 160 astronomical units away (an AU is the average distance from the Earth to the sun) and Voyager 1 is only 123.5 AUs away.

Florinski had some possible explanations for that as well. The sun has been pretty low-energy in its current 11-year cycle and perhaps it's not pushing the bubble as far as it once was.

Or - perhaps something else.

As Florinski said near the beginning of his talk: "These are my interpretations, so I take full responsibility for them, and they could prove out to be wrong."

So that's where Voyager 1 is - in a region where theory meets measurement and produces discovery.

On StarNet: View photos taken by Voyager I in space at azstarnet.com/gallery

Contact reporter Tom Beal at tbeal@azstarnet.com or 573-4158.

Copyright 2014 Arizona Daily Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Most Popular

Follow the Arizona Daily Star

Deals, offers & events

View more...
Get weekly ads via e-mail