• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

News From the Edge of the Solar System

Posted on: Sunday, 25 September 2005, 12:00 CDT

At the beginning of the edge of the solar system, the supersonic flow of energetic particles from the Sun _ the solar wind _ abruptly slows in a boundary zone called the "termination shock."

Readings collected by NASA's Voyager 1 spacecraft as it passed through the zone on its way to interstellar space last December show that the intensity of low-energy particles and magnetic fields increase sharply at the frontier, according to details published Friday in the journal Science.

But contrary to what physicists expected, the shock zone doesn't seem to increase the intensity of high-energy particles of helium, nitrogen, oxygen and other elements that have entered the solar system from other stars and are pushed along by the solar wind.

"When we go somewhere that is new, we find the unexpected, and that's what makes it so exciting," said University of Michigan space scientist Len Fisk in a Science commentary summarizing the technical findings.

"The termination shock doesn't perform as we expected," he wrote. "It is clear that it is a shock, but not the prodigious accelerator (of the high energy particles) that we expected."

Beyond a point that Voyager 1 has yet to reach _ perhaps the "bow wave" created by the entire solar system's movement through space _ may lie the source for the speed of the cosmic rays, the scientists now hope.

Although they're on different courses for deep space, Voyagers 1 and 2 have flown past the planets of the solar system since 1977. The slingshot path Voyager 1 took allowed it to reach the boundary some 8.7 billion miles from the Sun several years ahead of its twin and become the first human space probe to leave the solar neighborhood.

It's now inside a region called the heliosheath, a sort of buffer zone where the solar wind mixes with particles shed by other stars. It's a big mixing bowl, so big that it could take Voyager 1 another dozen years to cross before reaching a point in space where the pressure of gas from the rest of space takes control, and our Sun is just another star.

Voyager researchers first suspected the spacecraft was reaching the boundary in late 2003, when readings of magnetic energy started to soar, but only this spring did all members of the team agree that it had entered the heliosheath.

"Voyager's observations over the past few years show that the termination shock is far more complicated than anyone thought," said Eric Christian, a scientist with the NASA's Sun-Solar System Connection research program.

The space probe's instruments, although originally intended to operate for only five years, have mostly continued to function, although its plasma detector hasn't worked for years.

Scientists think the small nuclear generators on the craft could last another 15 years. When those fail, the Voyagers will continue to drift out in space, but won't be able to collect or transmit data. Both craft carry gold disks that contain symbols of life on Earth and recordings of greetings in several languages, as well as samples of musical recordings.

On the Net: http://www.sciencemag.org

www.voyager.jpl.nasa.gov/

(Contact Lee Bowman at BowmanL(at)SHNS.com. Distributed by Scripps Howard News Service, http://www.shns.com)

© 2005 Scripps Howard News Service.

All Rights Reserved.

Source: Scripps Howard

More News in this Category