Posted on 01/07/2004 8:18:43 AM PST by blam
Traveller must battle termination shock
January 07 2004 at 01:07PM
Popular Mechanics
Nasa’s seemingly unstoppable Voyager spacecraft is about to depart our solar system for interstellar space. This composite image shows the veteran spacecraft against the backdrop of the Sombrero galaxy, photographed by the Hubble Space Telescope.
Nasa's veteran traveller, Voyager 1, is about to make history again as the first spacecraft to enter the solar system's final frontier, a vast expanse where hot wind from the sun blows against thin gas between the stars.
However, before it enters interstellar space, Voyager 1 must pass through the termination shock, a violent zone where beams of high-energy particles are born.
Voyager's journey through this turbulent zone will give scientists their first direct measurements of our solar system's unexplored final frontier – the heliosheath. In fact, scientists are debating whether this passage may have already begun.
Two papers on the subject by American research teams were recently published in Nature: the first, by Dr Stamatios Krimigis and his team from the Johns Hopkins University Applied Physics Laboratory, provides evidence in support of the claim that Voyager 1 has passed beyond the termination shock.
'We have entered into a new part of the solar system' The second paper, by Dr Frank McDonald of the University of Maryland and his team, gives evidence against this claim. A third paper, published in Geophysical Research Letters by Dr Leonard Burlaga of Nasa’s Goddard Space Flight Centre and his collaborators, gives evidence that Voyager 1 has yet to encounter the termination shock.
Dr Eric Christian, Discipline Scientist for the Sun Earth Connection research programme at Nasa’s Headquarters in Washington, DC, puts the debate into perspective: "The Voyager 1 observations show we have entered into a new part of the solar system.
"Regardless of whether or not we have crossed the termination shock, the teams are excited because this has never been seen before."
He’s not the only scientist who thinks we should be looking at the bigger picture. Says Dr Edward Stone, Voyager Project Scientist at the California Institute of Technology: "Voyager 1 has seen striking signs of the region deep in space where a giant shock wave forms as the wind from the sun abruptly slows and presses outward against the interstellar wind. The observations surprised and puzzled us, so there is much to be discovered as Voyager begins exploring this new region at the outer edge of the solar system."
At more than 13 billion kilometres from the sun, Voyager 1 is the most distant object built by humanity. Launched on 5 September, 1977 it explored the giant planets Jupiter and Saturn before being tossed out toward deep space by Saturn’s gravity. It now approaches, and may have temporarily entered, the region beyond termination shock.
'The teams are excited because this has never been seen before' The termination shock is where the solar wind, a thin stream of electrically charged gas blown constantly from the sun, is slowed by pressure from gas between the stars.
At the termination shock, the solar wind slows abruptly from its average speed of 300 to 700 km/second.
The exact location of the termination shock is unknown, and it was originally thought to be closer to the sun than Voyager 1's current position. As the spacecraft cruised ever farther from the sun, it confirmed that all the planets were inside an immense bubble blown by the solar wind, and the termination shock was much more distant.
From about 1 August, 2002 to 5 February last year, scientists noticed unusual readings from the two energetic particle instruments on Voyager 1, indicating it had entered a region of the solar system unlike any encountered before.
This led some to claim that Voyager may have entered a transitory feature of the termination shock. Just as small bumps and "fingers" appear and disappear in the rough edge of the water flow over a plate in your kitchen sink, Voyager might have entered a temporary "finger" in the edge of the termination shock.
The controversy would be resolved easily if Voyager could still measure the speed of the solar wind, because the wind slows abruptly at the termination shock. However, the instrument that measures solar wind speed no longer functions on the venerable spacecraft, so scientists must use data from the instruments that are still working to determine whether
Voyager has pierced the termination shock. For their original missions to Jupiter and Saturn, Voyager 1 and its sister spacecraft, Voyager 2, were destined for regions of space where solar panels would not be feasible, so each was equipped with three radioisotope thermo-electric generators to produce electrical power for the spacecraft systems and instruments. Still operating in remote, cold and dark conditions 26 years later, the Voyagers owe their longevity to these generators, which produce electricity from the heat generated by the natural decay of plutonium dioxide.
The Voyagers were built by Nasa’s Jet Propulsion Laboratory (JPL) in Pasadena, California, which continues to operate both spacecraft.
Source: Nasa/Goddard Space Flight Centre
At its current speed, how long would it take Voyager to reach the nearest star (if it were aimed that way)?
I was arguing with my brother who claims it would be halfway there by now, with 26 years to go. I don't think its even close to that far out.
Voyager I is moving at about 3.6 AU/year, or 335,000,000 miles... The nearest star is about 4.3 light years away (about 25 trillion miles). At its current speed, it would take about 75,000 years to get there.
I knew my brother was insane.
The nearest star (Alpha Centauri?) is roughly 4 light-years away.
Almost got it. Proxima Centauri is the closest star. Alpha Centauri is the name of the three-star cluster of which Proxima Centauri is part of. And no, I don't have a life. ;)
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