Voyager 1 spacecraft approaches edge of Solar System


December 15, 2010

Artist concept of the two Voyager spacecraft as they approach interstellar space (Image credit: NASA/JPL)

Artist concept of the two Voyager spacecraft as they approach interstellar space (Image credit: NASA/JPL)

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The Voyager 1 spacecraft launched by NASA on September 5, 1977 continues to add to its impressive list of accomplishments. Its “Grand Tour" through the Solar System has seen it become the first probe to provide detailed images of the moons of Jupiter and Saturn and earn the title of most distant human-made object in the cosmos. After a 33-year journey, Voyager 1 has now crossed into an area at the edge of our Solar System where there is no outward motion of solar wind.

Now traveling at a speed of around 38,000 mph (61,155 km/h) and some 10.8 billion miles (17.38 billion km) from the Sun, Voyager 1 has reached a point where the velocity of the hot ionized gas, or plasma, emanating from the sun has slowed to zero. Instead of moving outward from the Sun, the solar wind has been turned sideways with scientists suspecting the cause to be the pressure from the interstellar wind in the region between stars, indicating the spacecraft is drawing closer to leaving the Solar System.

The sun gives off a stream of charged particles that form a bubble around the solar system known as the heliosphere. For the first 6.2 billion miles (10 billion km), the solar wind travels at over 0.62 million mph (over a million km/h), but slows down dramatically once it crosses a shockwave called the termination shock. This marks the start of the heliosheath, a region where the solar wind is slowed, compressed and made turbulent by its interaction with the interstellar medium.

Voyager 1 crossed the termination shock into the heliosheath in December 2004 and it took another three and a half years for the solar wind to slow to zero. This occurred in June this year, when Voyager 1 was about 10.6 billion miles (17 billion km) from the Sun.

Scientists used data from the spacecraft’s Low-Energy Charged Particle Instrument to deduce the solar wind’s velocity. When the speed of the charged particles hitting the outward face of Voyager 1 matched the spacecraft’s speed, they knew that the net outward speed of the solar wind was zero.

Because the velocities can fluctuate, the scientists watched four more months of reading to be convinced the solar wind’s outward speed had actually slowed to zero. Data also showed that the velocity of the solar wind slowed at a rate of about 45,000 mph (72,000 km/h) each year since August 2007, when the solar wind was traveling outward at a speed of about 130,000 mph (209,000 km/h).

The scientists believe that Voyager 1 has not yet crossed the heliosheath into interstellar space because that would result in a sudden drop in the density of hot particles. They currently estimate the spacecraft will reach that milestone in about four years but are putting data into their models of the heliosphere’s structure to determine a better estimate.

As with reaching the point where the velocity of the solar wind has slowed to zero, crossing into interstellar space will add yet another amazing feat to Voyager 1’s long list of achievements. It is estimated that Voyager 1 has enough electrical power to operate its transmitters until at least 2025, so the list is sure to keep growing for at least a little while longer.


About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

If you got buried out there..... Would anyone EVER come and visit?

Mr Stiffy

I loved this article but it was hard to read fluently because the writer kept jumping from imperial to metric with the other one in brackets.

I would prefer all measurements to be in metric because 99% of countries use the metric system. A far more sensilble system for measurements. My own country, Australia, went through the conversion in 1966. There was as you would expect a transition period when all the older citizens were converting in their heads, the old measurements.

I believe there was a major stuff up where the UK and the USA were working on a rocket program and the UK was working in metric and the USA worked in feet.

I now know that most scientists in the US use metric so why not get the whole country on board and join the rest of the countries.

Article has been updated to make order of units consistent. Ed. Lawrie Barclay

Surely Web 2.0 should support \"read in your own units\"? Then provincials can use miles, most of us can use kilometres, and the central country can use li, without distraction.


A couple reasons why we don\'t switch over to metric is because: -Everyone here is using the imperial system of measurements. We\'re one of the few countries that still uses the system, and we might keep it for that reason alone. -(The Biggest) Because the cost of changing things would be unfathomable. Billions would be spent because we have millions of road signs alone that use the imperial system. All of those billions would be from just the tax payer\'s money. We can\'t afford that at the moment because we\'re one of the most broke countries in the world now, and we have more important things to spend our money on (education, roads, NASA, etc). Even if we were out of all debt and had money to spend, changing EVERYTHING would put us back into debt.


I noticed that the article says that Voyager has enough power to continue to transmit until 2025 and it\'s been operational since 1977, we still can\'t build a decent electric car?


\"everyone is doing it...\" \"get on board\" \"sensible...\" This is flawed thinking at it\'s finest. mate.

English measure is inherently tailored around the human condition and is not like metrics, an artificial contrivance that might suit scientists but fails the day to day relationship that people have with their world.

Take Celsius. Might be fine for robots but for people you must squeeze yourself into a rather confining 30 or so degrees not so with 0º F. Here you know it is hot at 100º and very cold at 32º. 72º is just peachy. Even science ditches Cº when dealing with absolute temps.

In building, we logically use feet and inches and seldom yards. And here fractions shine. In fact the world is parted in fractions. 8 fingers and 2 thumbs by the way. And people in yards, never as feet and inches are perfect.

You Aussies use Nautical Miles do you not? Why? Feet are used for altitude and not yards by reasoned choice.

In fluid measure, gallons are used not quarts for fuel. And fluid ounces mean something to humans.

During WW2, English measure was just peachy in defeating the Germans and Japanese. Von Braun had no problem using such to send humans to the Moon... .

I could go on by I am running out of time, something else that is NOT metric. As a SUBJECT to your State you really don\'t have much of a choice in doing so many things so if the State wishes to be like Lemmings, so be it mate. Alex has some good points too.


Naaaahhh... actually, the reason we don\'t change over to metrics here is because the tools at the top (read that metaphorically if you must) aren\'t capable of real change. If they were, the government wouldn\'t own two of three of our primary automotive manufacturers. This excuse has been around for years. In the words of Nike: \"Just do it!\"


we knew this was cool back in 1977. how very cool is it now!

Booth McKeown

@ lwesson

I couldn\'t disagree more. I grew up in the metric system; it\'s as real, human and tangible as it gets. When someone says a measurement in metric like \"98.5mm\" it makes instant sense. When someone rhymes off something like \"1 and 5/16th\" it pure gibberish. Inputting fractions into a calculator, computer or etc is a huge hassle. Decimal points over fractions any day.

Temperature metric makes sense. 0 is water freezing, 100 is it boiling and 30 is stinking hot. If you want to get more out of Celsius you just make use of decimals. Easy. Having freezing at -32F and boiling at 212F is crazy. Lots of unnecessary math in there.

There\'s a reason why scientists, even in the USA, switched to metric ages ago. It makes sense.

Flying Crowbar

Let\'s switch to the Réaumur_scaleéaumur_scale Or perhaps Rankine?

How the Voyager probes have kept going so long is with RTGs or Radioiosotope Thermal Generators. They have a core of radioactive material, surrounded by a large number of stacked Peltier junctions. It\'s the reverse of the same process used in solid state electric coolers where a voltage applied across a Peltier junction causes heat to be moved from one side to the other.

Of course there\'s inefficiency so the hot side has an excess of heat compared to how much heat is being absorbed by the cold side.

Heating one side of the junction while cooling the other causes a voltage to be produced. I suspect there are optimizations of the design for producing electricity from temperature differential VS designs optimized for moving heat with electricity.

When RTGs were first used one name for them was SNAP or System for Nuclear Auxiliary Power, but it had that word \"Nuclear\" in it so they got renamed RTG.

Facebook User

Flying Crowbar, is the name something to do about getting someone to come along?

Human ergonomics was the whole point per my English measure missives. 98.5cm starts to get into too many of those little centimeter things to quickly visualize. In the house that I built, we used inches in small applications and feet and inches in others. Never did we have some issue with fractions. Saying it is gibberish does not mean that it is gibberish just because you said it but that seems to be the way that the Metric misanthropes reason. Just do it. Do it or die. That happened in France. Do it or go to prison or get fined. England It seems that Metric must have the strong arm of the Police State to get people to use it. Curious.

Again, Fahrenheit was designed around the human condition. And again the point is missed that Cº forces a compression of habitable conditions into a tiny confine. Loved the link to Re\'aumur scale FB User. And there is Kelvin, why not if you use Cº just go and ahead and use Kelvin as scientists use it and if they use it then it is good for the rest of us?

If metric was so radically superior, it would seem that serious change during times of war to win a war or a Moon race... it would have been snapped up.


@ Iwesson google the flying crowbar, it\'s pretty cool.

One of the reasons scientists use it is because they have to. No, not by force, but because English Imperial is so archaic is has no measurement in certain fields. Think electricity, magnetism and radiation. I\'m sure an \'ounce\' of electricity might sound more human to some; but I\'ll stick to Watts, Amps and Volts.

You\'re asserting that ºF is more human or ergonomic than ºC; on opinion. I disagree. Even the J/K students know 0ºC is when it\'s chilly enough for water to freeze and 30ºC is very hot out. If 4-5yr old\'s can pick it up almost instantly there must be something simple, human or ergonomic going for it. No point missed, ºC doesn\'t force anything, use a decimal if you must. The Princess and the Pea might be able to notice differences of 1ºF, for the rest of us 1ºC increments in temp will suffice. Scientists can use ºK; it works best for them.

\"If metric was so radically superior... would have been snapped up.\" \'Dont change horses mid-stream\' comes to mind.

Von Braun designs state weight in metric tons... only because he used metric. Anyone that can use the base 10 number system can pick up metric easily.

Flying Crowbar

I think anyone who is reading these posts, should be able to move from metric to english. particle to wavicle, abstract to real, without comment. This should be life on the finge and open to all concepts.

Facebook User

@kia00, In order for Voyager I\'s power to last as long as it has, think \"nuclear\"! Now, that would not be a good thing for EVs to be touting around, would it?

Will, the tink

Amazing !!! How the small minded we are....Here we have this incredible stuff happening and we are debating the merits of metric vs. imperial !!! Nick the Russian

Nick The Russian

Amazing !! Through modern \"Miracles \" we are made privi to this magical stuff happening in our life time and as a total insult to human race we are concerned about the units of measurement !!!!! Surely you can\'t be for real !!!

Nick The Russian

It truly is amazing to think a space craft that is older than most of the population of Africa is still sending us data. This says a lot about our world and our ability to solve problems, both negative and positive.

Hum... metric vs. imperial, star wars vs. star trek, Mac vs. PC, aluminum vs. aluminium... hurrah for arguing on the internet. It is a good argument, however, so here\'s my 2 cents.

I use both systems of units. I grew up working for a contractor in the US, and I can estimate things in feet, inches, lbs, and degrees F to within a workable level of detail. I also have a pretty good feel for pints, gallons, and mph. Not surprisingly, I have no trouble estimating a meter or cm, liter or ml, gram or kg, or degree C as these are measurements that anyone who uses foreign made parts, goes to the gym, purchases soda, or takes a science class has to deal with on a regular basis. Also, a cm is about the width of my thumb, so it\'s a bit easier to use than an inch. I still have to convert k/h in my head when I travel, but it\'s not so bad.

Both systems are perfectly adequate (and seriously, I have seen decimal inches and fractional cm on plenty of occasions - they both work both ways). So really this comes down to the argument of old vs. new. In the \"old\" camp, the main argument seems to be about money and unwillingness to learn something new. In the \"new\" camp, people feel that one is patently better than the other because \"it makes more sense\". Both of these arguments are flawed. Metric doesn\'t make more or less sense than \"English\" units for most applications, and where it does people already use it. By the same token, however, a growing portion of our parts and machines already are tooled to metric (because it\'s cheaper to design something that works on the part produced in Japan or Germany than to build something to make the standard units version here). The idea that we couldn\'t slowly change our road signs (and maybe welcome in some outside money as more tourist friendly) to showing both km and miles is also silly - if we made it a 15 year project then we would be able to replace most signs just on a maintenance basis. Finally, as the richest country in the world, the idea that we can\'t pay some up front cost for a project that has clear long term cost saving benefits (bringing jobs back to the US because countries don\'t have to translate to use parts they get from us for instance) is pretty silly.

The US has bigger problems to deal with, for sure, but in the end a conversion plan would be a cost savings plan and is something that entrepreneurs should be pushing for, not shutting down.

Charles Bosse

If it wern\'t fer Ol Jimmy Carter deciding that we needed to change our system of measurement to match that of Europe, soon they would have been forced to adopt our U.S. system. It is not \"imperial\" that is what was used in England. The greatest accomplishment from this has been to facilitate those importing foreign goods. For the rest of us it is a Pain in the wallet. It causes massive errors in measurement on a daily basis. For myself I cannot count the times I have misread a tape measure because I was working in low light and reading it upsidedown and backwards and accidentally used the metric edge of the tape instead of the standard side. Now I have metric sockets / standard sockets , metric thread tools / standard thread tools, metric micrometers / standard micrometers, metric calipers / standard calipers, and the list goes on. Now I keep pocket calculators in the tool boxes to help when converting from standard to metric and back. I hope that it is taught in school to my grandchildren just how big of a screw-up Jimmy made when he decided to force the rest of the world onto us Americans. Our system is more natural and easier to work with in your mind. It is based on halves. Half of a half is a quarter and all. It is easier than a ten based system. My conclusion is that forcing metrics onto us is a complete disaster. Part of the problem is that in our country it is not dictated by the government what system will be used. The government deciding is like the tail wagging the dog. Industry had made it\'s decision and we used the US system of measurement which was derived from the better parts of some older systems and we refined it. Now like many examples of government action we have a totally screwed up system but if you are part of this industry or that industry you will be forced to comply with Jimmy\'s mandate and if you are not part of any industry you must deal with a two system system of measuring. I hear lots about Jimmy Carter and Habitat for Humanity. I would like to hear more about how Jimmy damaged the US infrastructure with his desire to make us more like socialist Europe

David Cordon

Our U.S. money is metric. We ditched the cumbersome English monetary system very early, because the metric monetary system is better (would you really prefer to count money in pounds and shillings? pennies and ha\' pennies? and what the eff is a \"crown\" or a \"half-crown???). We do have a significant investment in the English system of measures, and wholesale, forced conversion would be expensive and pointless. Better to let market forces make the transition gradually: I buy bottled water in 16.9 oz bottles- which happens to be the exact same as 1/2 liter (500 ml). I buy sodas in \"2-liter\" bottles (67.6 oz, sorta roughly equivalent to a half-gallon: 64 oz).

I think the answer lies in dual labeling for a period of time, metric and English, and let the consumer eventually decide which system they prefer. No pointless and divisive drama, no political \"demonizing,\" just market forces at work.

William Lanteigne

I have some thoughts on the matter. I think not only should we abandon the old system, I think globally, we should scrap our time keeping techniques too. 100 seconds to the minute, 100 minutes to the hour, 10 hours to the day and so on.. Maybe the Mayan calendar system? Not sure on the calendar..maybe there is a better system someone else has devised. Metric only makes sense for other measures IMHO... The conversions make it so much easier...what arbitrary numbers...5280 feet to a mile, 12 inches in a foot...4 quarts in a gallon? C'mon.. and the fractions? I'm over it.. Metric and decimal all the way. Really, we should switch, and England and her old colonies should drive on the correct side of the road

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