A quick note: Voyager nears the edge....

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Thirty five years ago the Voyager 2 space craft [1] was launched. With its sister ship, it opened up a new solar system for us. It revealed the clouds, and moons, of the giant planets as never before. It showed us the volcanoes of Io, the smogs of Titan, the enigmatic moons clustering around Uranus and Neptune.

Image above: One of the volcanoes of Io, among the Voyager missions greatest discoveries, blows sulphur based lava into the moons sky. Beautiful. From my armchair. Up close, probably a brown trousers experience, although a short lived one. Image courtesy of NASA/JPL.

It may be about to make another first: First space ship to reach interstellar space.

Almost 18 billion kilometers from Earth the stubbornly long lived probe is showing signs that it is about to leave the heliopause [2], the edge of the Suns magnetic field.

The grandaddy of space probes had already reached the 'stagnation region'[3], where the solar wind starts to loose speed, and the solar magnetic field starts to pile up..
Clues that the edge is coming up fast have been arriving, as a steady rise in the number of hits from high speed cosmic particles, since 2009. These are microscopic debris from supernova explosions, debris that our Suns magnetic field keeps out of the solar system. The number of hits has increased by nine percent in the last month, and Voyager controllers are waiting for the final confirmation that Voyager has broken through -  a change in the direction of the magnetic field lines surrounding the little ship from east-west to north-south.


Video above: The story of the Voyager mission, as told by the people who've worked on it. Be warned it's almost an hour long, but well worth it if you have an hour to spare. Go on, get a glass of wine and a bar of chocolate and give it an hour. Video courtesy of NASA/JPL.

Although there's not much to see that far out - well there's the majesty of the entire Universe on display, but aside from that not much - scientists have been hoping to see Voyager become our first toe dipped into interstellar space for a long time. Before the event it is impossible to say for sure when the crossing will occur, and Voyagers on board nuclear batteries will only be able to keep it alive out there for so long. The penciled in date of possible last contact with the probe is 2025.
That seems a long way off, but then so does the deadline for my tax return, and I know from past experience what a mess I can get into with that one.

Image above: The IBEX ribbon. The IBEX mission, designed to monitor the incoming neutral particles from the solar systems boundary, found a 'ribbon' of higher energy particle emission.  The image above is an 'unwrapped' full sky image, with higher energy particles shown in yellow to red and lower energy particles shown in green to blue. Image courtesy of NASA.

It's not just the 'first to' that has space nerds excited: The exact nature of interstellar space has been tantalizing us. There was the discovery of the IBEX ribbon [4] by the Interstellar Boundary EXplorer craft [5], and the discovery the gas in interstellar space is much more strongly magnetized [6]than expected. The strong magnetic field and the ribbon may well be related, with the field reflecting energetic solar particles to create the ribbon [7]. It all adds up to... well, no-one's quite sure. But the thinner-than-thin gas between the stars is the stuff that goes into the molecular clouds, that birth the next generation of stars So understanding it is the root of understanding our solar systems history.

What we do know is that we don't yet fully understand the way interstellar space works. And Voyager, it seems, will soon be able to experience it first hand....

List of links:
[1]http://voyager.jpl.nasa.gov/index.html
[2]http://en.wikipedia.org/wiki/Heliosphere
[3]http://voyager.jpl.nasa.gov/news/new_region.htm
[4]http://phys.org/news194079881.html
[5]http://ibex.swri.edu/index.shtml
[6]http://science.nasa.gov/science-news/science-at-nasa/2009/23dec_voyager/
[7]http://science.nasa.gov/science-news/science-at-nasa/2010/15jan_ibex2/