preview.tinyurl.com/2w2wlk -> space.newscientist.com/article/dn13029-voyager-2-probe-reaches-solar-system-boundary.html?feedId=online-news_rss20
Advertising The Voyager 2 spacecraft has crossed an important space frontier called the termination shock, and in a few years may become the first object made by humans to travel outside the solar system. NASA's two Voyager spacecraft were launched in 1977 to tour the outer solar system. They are now far beyond the orbits of the outermost planets and heading towards interstellar space.
There, the solar wind made of charged particles from the Sun suddenly falters as it feels pressure from gas in the interstellar medium lying outside the solar system. But scientists missed observing the crucial moment because the sensitive radio dishes on Earth needed to hear the spacecraft's transmissions did not happen to be listening at the time.
Cassini, and therefore cannot listen to the Voyagers around the clock. The Voyagers cannot store their observations onboard, so they are lost forever if they are not relayed to Earth as they are made. Now, Voyager 2 has crossed the same boundary, and this time scientists were lucky enough to be listening when it happened. Pushing the boundary The spacecraft crossed the boundary on 30 August 2007 at a distance of 84 astronomical units (AU) from the Sun (1 AU is the distance between the Earth and Sun). "We were very lucky this time," Voyager chief scientist Edward Stone of Caltech in Pasadena, California, US, told New Scientist. Voyager 2 actually crossed the boundary five times (and was directly observed making the passage three of those times). That is because the location of the termination shock is constantly changing in response to the Sun's activity. Plasma burps from the Sun called coronal mass ejections (CMEs) temporarily push the boundary outwards, for example, so that it washes back and forth over the spacecraft like a wave on the beach. An instrument on the spacecraft measured the abrupt slowdown of the solar wind that defines the termination shock. Sapped energy But the shock did not look the way it was expected to. Instead of seeing a very abrupt drop, the spacecraft saw a gradual slowing of the solar wind ahead of each crossing, followed by a relatively small drop at the termination shock itself. Mission scientists are not sure how to explain the gradual slowdown preceding the shock. But Stone says neutral atoms from beyond the termination shock may be interacting with the solar wind to produce speedy charged particles called cosmic rays, thereby sapping some of the wind's energy. Voyager 1 and 2 are now both in a region of slower solar wind lying past the termination shock called the heliosheath. That region ends at the heliopause, which is where the solar wind ends and interstellar space begins. One or the other of the spacecraft will become the first probe to reach interstellar space after a travel period Stone estimates to be about 7 to 10 years long. It is not clear which spacecraft will be first, even though Voyager 1 is about 20 AU farther from the Sun than its sister spacecraft. Squashed solar system Now, scientists know that the termination shock is 84 AU from the Sun in the direction Voyager 2 has traveled 10 AU closer than in Voyager 1's direction.
boundaries are squashed in one direction because of the influence of the interstellar magnetic field. Depending on how squashed the heliopause is, Voyager 2 could leave the solar system first. On the way, the Voyagers could help determine the source of mysterious radio emissions from the edge of the solar system, which may be the result of CMEs from the Sun crashing into the interstellar medium. Gary Zank of the University of California in Riverside, US, who is not a member of the team, says the distant Voyagers are providing a unique opportunity to study the interaction of the solar wind with the interstellar medium. "It's taken the Voyagers 30-odd years to get to this region of space," he told New Scientist. For the very first time we're really beginning to study how winds interact with the interstellar medium, and we're doing it in situ." Add a comment Comment subject Comment No HTML except lower case italic tags or lower case bold tags, please: <i> or <b> Your name Your email We need your email in case we need to contact you about the comment.
VIEW THREAD >> Voyager 1 And 2 By Richard Mon Dec 10 19:29:40 GMT 2007 I remember these being launched many years ago, and shone my torch into the night sky to see which would get to the stars first first - Voyager or my photons!
VIEW THREAD >> Voyager By Martin Mon Dec 10 19:48:50 GMT 2007 Great to hear that the Voyagers are on their way into interstellar space - quite a surprise that they are both still functioning after all this time!
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