Voyager makes an interstellar discovery

Voyager makes an interstellar discovery
Voyager flies through the outer bounds of the heliosphere en route to interstellar space. A strong magnetic field reported by Opher et al in the Dec. 24, 2009, issue of Nature is delineated in yellow. Image copyright 2009, The American Museum of Natural History.

The solar system is passing through an interstellar cloud that physics says should not exist. In the Dec. 24th issue of Nature, a team of scientists reveal how NASA's Voyager spacecraft have solved the mystery.

The solar system is passing through an interstellar cloud that physics says should not exist. In the Dec. 24th issue of Nature, a team of scientists reveal how NASA's have solved the mystery.

"Using data from Voyager, we have discovered a strong magnetic field just outside the solar system," explains lead author Merav Opher, a Heliophysics Guest Investigator from George Mason University. "This magnetic field holds the interstellar cloud together and solves the long-standing puzzle of how it can exist at all."

Voyager makes an interstellar discovery
An artist's concept of the Local Interstellar Cloud, also known as the "Local Fluff." Credit: Linda Huff (American Scientist) and Priscilla Frisch (University of Chicago)

The discovery has implications for the future when the solar system will eventually bump into other, similar clouds in our arm of the .

Astronomers call the cloud we're running into now the Local Interstellar Cloud or "Local Fluff" for short. It's about 30 light years wide and contains a wispy mixture of hydrogen and helium atoms at a temperature of 6000 C. The existential mystery of the Fluff has to do with its surroundings. About 10 million years ago, a cluster of supernovas exploded nearby, creating a giant bubble of million-degree gas. The Fluff is completely surrounded by this high-pressure supernova exhaust and should be crushed or dispersed by it.

"The observed temperature and density of the local cloud do not provide enough pressure to resist the 'crushing action' of the hot gas around it," says Opher.

So how does the Fluff survive? The Voyagers have found an answer.

"Voyager data show that the Fluff is much more strongly magnetized than anyone had previously suspected—between 4 and 5 microgauss*," says Opher. "This magnetic field can provide the extra pressure required to resist destruction."

NASA's two Voyager probes have been racing out of the solar system for more than 30 years. They are now beyond the orbit of Pluto and on the verge of entering interstellar space—but they are not there yet.

"The Voyagers are not actually inside the Local Fluff," says Opher. "But they are getting close and can sense what the cloud is like as they approach it."

Voyager makes an interstellar discovery
The anatomy of the heliosphere. Since this illustration was made, Voyager 2 has joined Voyager 1 inside the heliosheath, a thick outer layer where the solar wind is slowed by the pressure of interstellar gas. Credit: NASA/Walt Feimer.

The Fluff is held at bay just beyond the edge of the solar system by the sun's magnetic field, which is inflated by into a magnetic bubble more than 10 billion km wide. Called the "heliosphere," this bubble acts as a shield that helps protect the inner solar system from galactic cosmic rays and interstellar clouds. The two Voyagers are located in the outermost layer of the heliosphere, or "heliosheath," where the solar wind is slowed by the pressure of interstellar gas.

Voyager 1 entered the heliosheath in Dec. 2004; Voyager 2 followed almost 3 years later in Aug. 2007. These crossings were key to Opher et al's discovery.

The size of the heliosphere is determined by a balance of forces: Solar wind inflates the bubble from the inside while the Local Fluff compresses it from the outside. Voyager's crossings into the heliosheath revealed the approximate size of the heliosphere and, thus, how much pressure the Local Fluff exerts. A portion of that pressure is magnetic and corresponds to the ~5 microgauss Opher's team has reported in Nature.

The fact that the Fluff is strongly magnetized means that other clouds in the galactic neighborhood could be, too. Eventually, the solar system will run into some of them, and their strong magnetic fields could compress the heliosphere even more than it is compressed now. Additional compression could allow more cosmic rays to reach the inner solar system, possibly affecting terrestrial climate and the ability of astronauts to travel safely through space. On the other hand, astronauts wouldn't have to travel so far because interstellar space would be closer than ever. These events would play out on time scales of tens to hundreds of thousands of years, which is how long it takes for the solar system to move from one cloud to the next.

"There could be interesting times ahead!" says Opher.

To read the original research, look in the Dec. 24, 2009, issue of Nature for Opher et al's article, "A strong, highly-tilted interstellar magnetic field near the .

Explore further

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Dec 26, 2009
the comeback of plasma cosmology?

I wouldn't say Alven was completely right in fact he made some incorrect observations as well, but he wasn't completely wrong either. Electromagnetic forces are out there with gravity, they aren't mutually excluswive so we shouldn't be limited to a standard model or a plasma model, theres is hybridisation on many levels and scales.

Dec 26, 2009
at least the scientific advances in instruments and telescope and computational power regarding magnetohydrodynamic flows allows us to observe and calculate that electromagnetic forces play a bigger part in the evolution of the universe than we were able to observe / account for than in the past.

Dec 26, 2009
This comment has been removed by a moderator.

Dec 26, 2009
maybe the missing mass and dark matter might be explained by plasma cosmology.

Dec 26, 2009
What are the odds this 6k C cloud is having an affect of warming our environment? It looks like we entered that cloud 'recently'.

Dec 26, 2009
What are the odds this 6k C cloud is having an affect of warming our environment? It looks like we entered that cloud 'recently'.

What are the chances the voyager's will survive once hey move beyond the protective heliosph

Dec 27, 2009
There is no "interstellar cloud that . . . should not exist."

What is, . . . is!

What is cannot be changed!

Hopefully, physics can.

With kind regards,
Oliver K. Manuel

Dec 27, 2009
we entered this local fluff ~150k years ago. So don't think we're entering new one.

Dec 27, 2009
So this would this offer some protection against a local star going nova?

Dec 27, 2009
This IS protection against 'local stars' having gone nova in the distance (for us...) past ;P, on an interstellar scale it's still 'current'.
I had a giggle at the climate change comment, 170000 years we've been in this cloud.

Dec 27, 2009
Great comments, I particularly like the one about climate change. It makes sense that if something is compressed it's pressure and temperature would increase. But if we've been in this cloud for approximately 170000 yrs. why are we only just beginning to see Earth's changes? Or, have we not been paying attention? Maybe we should begin looking at historical, geologic and mythical data/records. We may be surprised at what we find. Just a thought.....

Dec 28, 2009
I am new to this community. In reading all of the comments about this article I must say that I find it refreshing that there are so many intelligent people reading PhysOrg! Thanks for all of your comments!

Dec 28, 2009
There are a striking number of situations which, together, have allowed life to evolve on earth. The sun protecting us from the fluff, and the earth's magnetic field protecting us from the sun, and Jupiter protecting us from the asteroid belt, and the fluff protecting us from the supernovae. The ingredients for life may well be strewn about everywhere, and life itself may get started with the least amount of opportunity, but we are learning what it takes to evolve uninterrupted for 4.7 billion years, and it may take a very special situation. The fact that we have been listening, attentively, for any sign of life, and we have found none whatever has physicists taking pause. To destroy this earth by polluting our water, air, and soil, in just over 100 years is sacrilege.

Dec 28, 2009
Could a manned spacecraft safely fly through these interstellar clouds? Can someone offer a good comparison for the strength of the interstellar cosmic radiation? And at what spacecraft speed might the density of the local interstellar material begin to impede travel or become an issue?

I'd appreciate any response or direction to other sources for the answers. Thanks.

Dec 28, 2009
Who hoo! Magnetic intestellar travel here we come! Sailing the mag clouds like ocean currents. I wonder if we have magnetic trade winds and doldrums. This is awsome. It could also explain some of the Tesla ether he was tapping into. Its the turn of the century with discovery all over again! Candy for the brain.

Dec 28, 2009
why are we only just beginning to see Earth's changes

You are aware that earth's climate has been in a constant state of nothing but change for the past 4 billion years of it's existence, right? That the one certainty regarding global climate is that it will change?

I mean, you don't really believe that change in climate is anything new or even something to consider as a threat, do you? Much like omatumr said, it simply is.

Nah, you're certainly able to see that our inability to adapt to a changing climate is the only thing to be afraid of. And correspondingly that all proposed "carbon shuffling" legislation actually promotes continued reliance on fossils and obscures the importance of adaptability, and supporting that goal directly.

Certainly you've put more thought into the matter than what the powers that be have fed you. Yes?


Dec 28, 2009
Lot's of good stuff to end the year with!! How about those two little spacecraft? Still truckin' and communicating! Still more good stuff to learn, while we sweat under even more G/Warming. Get used to it, folks. It's the nature of the Universe. Happy New Year to all.

Dec 28, 2009
For gods sake, you pro-/anti-global warming posters, just because the gas cloud is at 6000K doesn't mean a thing! Gas temperature is a measure of the average speed of the molecules. Sure, those hydrogen and helium molecules are moving fast, but there are very few of them per cubic meter. That cloud of gas is probably a better vacuum than we can make on Earth. If a few high-speed molecules hit you, you won't get hot. Heck, you won't feel a thing. To get heat transfer, you need high energy density, not just high temperature.


Dec 28, 2009
It's amazing the two Voyager spacecraft are still operational after all these years! It's even more amazing we can find their minute signal from this far away. If they can stay working long enough to get to interstellar space - what an accomplishment. I bet the engineers who built them are patting themselves on the back. In his Cosmos series, Carl Sagan said that all the energy from all the radiowaves recieved on earth from the heavens in modern radio telescopes is less than the energy of a single snowflake gently settling to earth. Great stuff!

Dec 29, 2009
Magnetised hydrogen... fascinating. How was it magnetised? Is this "local fluff" behaving as if it's a BEC, or something? What are the optical effects?

Dec 29, 2009
Still giggling eh? What science "knows" about the universe and fifty cents couldn't buy a cup of coffee at dawn donuts. Really, such arrogance. Try to remember that everything that could be discovered about physics had been accomplished by 1901, so said the "great minds" of science at that time.Despite your "advanced" education, you have sadly missed the entire point of science; The questions are more important than the answers. The questions basically stay the same, it's the answers that change. So please, don't berate the curiosity of those who clearly show more wisdom than you; who already know everything. Good luck with your career, as thoughtfulness seems to missing from your resume. You must be a college professor.

Dec 29, 2009
Good luck with your career, as thoughtfulness seems to missing from your resume. You must be a college professor.

Please pardon my asking, but to whom are you referring?

Dec 30, 2009
I suppose that was a bit over the top, and I apologize if it is taken personally, I guess my point is that science sometimes talks and looks down on the "little people" when in fact throughout the history of science they are continuously wrong, wrong, wrong, until...they get it right. Science has nothing to brag about when it comes to understanding the facts.

"I had a giggle at the climate change comment, 170000 years we've been in this cloud."

I don't like to see comments like this cause it reminds of sciences dubious past. Ice ages, plate tectonics, Copernicus and Galileo all ridiculed or worse, by people well versed in the science of the day. Let us all resolve to be a little more humble(myself especially!)when the issue of what we know vs. what we understand comes up.
All hail the glorious data, highest of praises to the keepers of the math.
In Einsteins name we pray,

Dec 31, 2009
Two questions:

First, what is the density of this cloud? Temperature (6K C) and heat ARE NOT the same thing.

Second, do we know, at this point, whether this cloud is the source of the Cosmic Background Radiation?

Dec 31, 2009
As I agree, "The questions are more important than the answers"; Of the reference stars in the second picture, is there any record of any increase and/or decrease of output?

If one to propose that stars assume their energy from their environment, any observable changes in that environment should manifest in output of the star.

Dec 31, 2009
I would also like to point out to anyone wondering if this cloud is effecting the global climate, that even if it did have a very high specific heat, it would be difficult to conduct this energy through the near vaccuum of space. As the article mentions, the magnetic field of the sun keeps the cloud out out of the solar system.

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