Space

Voyager 1 spacecraft approaches edge of Solar System

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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Artist concept of the two Voyager spacecraft as they approach interstellar space (Image credit: NASA/JPL)
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Artist concept of the two Voyager spacecraft as they approach interstellar space (Image credit: NASA/JPL)
Voyager spacecraft (Image credit: NASA/JPL)
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Voyager spacecraft (Image credit: NASA/JPL)
Voyager spacecraft (Image credit: NASA/JPL)
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Voyager spacecraft (Image credit: NASA/JPL)
Voyager spacecraft before launch in 1977 (Image credit: NASA/JPL)
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Voyager spacecraft before launch in 1977 (Image credit: NASA/JPL)
Voyagers path to the edge of the solar system (Image credit: NASA/JPL)
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Voyagers path to the edge of the solar system (Image credit: NASA/JPL)

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.

Voyager spacecraft (Image credit: NASA/JPL)
Voyager spacecraft (Image credit: NASA/JPL)

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.

Via NASA

20 comments
Mr Stiffy
If you got buried out there..... Would anyone EVER come and visit?
Lawrie Barclay
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.
Geometeer
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.
AlexBizzar
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.
kia00
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?
lwesson
\"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.
MJRydsFast
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!\"
Booth McKeown
we knew this was cool back in 1977. how very cool is it now!
Flying Crowbar
@ 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 -32*F and boiling at 212*F 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.
Facebook User
Let\'s switch to the Réaumur_scale http://en.wikipedia.org/wiki/Réaumur_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.
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